My own impression is that some of the prolific writers do indeed lose steam when writing a long stream of novels, but then sometimes catch their breath and again produce a novel up to their old standard, and sometimes several. In other words, the quality may be uneven, but generally does not go away altogether. My DH and I read Sue Grafton, Elmore Leonard, Carl Hiaasen, and until they died this past year or two, Dick Francis and Robert Parker. We found this to be true of all these authors. The first one of us to read a new book will pass it along to the other saying either, "It was okay, not one of the best", or "Really good one, just like the old ones; you'll really like it."

We'll really miss Dick Francis and Robert Parker. They seemed like old friends to us, and you forgive the minor flaws of old friends. That sense of friendship with a writer whose work you have been reading for years is deceptive. It's actually why I am hesitant to meet writers whose work I really love. I don't want to come off as the crazed fan stalker lady, or even (more likely) someone who is presumptuously friendly.

I am sorry to say that occasionally a writer stops producing any books I like at all. When it is a writer whose older works were genuine favorites, this is very saddening. Not only are you missing the experience of enjoyable reading, but you are somehow severing the imaginary relationship. It is an estrangement as well as a loss.

Rosefolly

I miss Georgette Heyer, nobody seems to be able to write a Regency romance or mystery with the same deft touch.
Of course I read all of Grafton and she has gone back to her simple roots after a couple of books in the A-Z series got bad reviews.
Also I collect Evanovich, in and out of the numbers series.
Again, she has a unique style. I have not come across another light mystery writer who makes me laugh so much!

Even Navada Barr has a clinker now and then, but I love her all the same! Another I'm thinking of is John Grisholm....love most of his books, but now and then there will be a clinker. We do think our favorite authors should go on and on making us happy, but that is not realistic, I suppose.

Well Cynthia Harrod-Eagles has to be my main one - up to book 31 in the Morland Dynasty and not a poor one among them. I also read her Bill Slider mysteries - the mystery bit varies from good to so-so, but the personal interactions and humour are always good.
I have a complete Dick Francis collection, and Agatha Christie, but of course no more from either of them, alas.
I gave up on Grafton and Cornwell - just didn't like or care about the characters any more.
There are a few authors who, in my opinion, are just going overboard with the number of books they produce, including James Patterson and Alexander McCall Smith. I know that many readers are beginning to be put off by the number of books they need to purchase to keep up with these series, and it may in the end be to the authors' detriment. It also means you lose the excitement of the 'one book a year', and looking forward to it.

Cynthia H-E is one of my favorites, too, as was Dick Francis. I like Margaret Maron, Anne Perry, Martha Grimes' Jury series, and James Lee Burke. I still buy Elizabeth Peters just because I have all her others. I loved Janice Holt Giles who began a family chronicle set in pioneer Kentucky but died before she got the fictional descendants all the way to California. Her early books are far the best to me. She got so she wrote beautiful books but forgot to tell a good story. She wrote a number of non-series books, and most of them are very good.

astrokath-I heartily agree with you on Harrod-Eagles. I own every one of the Morland books, some bought at considerable cost to myself, but I love every one. As soon as a new one comes out I order it from the UK. My mother who is 88 and in poor health loves all of them too and worries she will die before the next one comes out!
I have a few other authors who I continue to find their books well done but after writing about Ms. Cynthia I cannot class them in the same post.
I did try her B. Slider books and really wanted to like them but don't.

Pam, I think the Slider books are very Commonwealth-oriented. There is a lot of rhyming slang and the sort of humour that I find very British, so they might not travel the Atlantic as well as the Morland ones.

James Lee Burke
David Baldacci
Sharyn McCrumb (The last few have been uneven.)
Margaret Maron
Elizabeth Peters (I'll give her one more novel. The last was just awful.)
Janet Evanovich's Plum series (Picked up an early Evanovich at Mom's house and found it unreadable. I'm not tempted by her other work.)

I'd given up on Cornwell, but picked up a new one at a relative's house and found I really liked it. It was less burdened by sexual identity that some of the more recent.

Gave up on Grafton after S & T which I listened to back to back. I slept through hours of them and didn't miss anything.

I don't like Reichs, but somehow I keep reading them.

I agree, most prolific writers begin to write the same old thing and not so very interestingly.

Tony Hillerman - who died last year. I loved all of his books about tribal cops Joe Leaphorn and Jim Chee. These are the only books I have ever collected.
Dick Francis - not sure I've read them all, but I like what I've read. Just read one he wrote with his son.
Georgette Heyer - Just started reading her based on RP recs.
Grimes - Read her early Jury books and loved them. Lost interest later in the series.

Non-mystery authors - not series
Alice Hoffman - really enjoy most of her books
Anne Tyler - love her writing and characters
Christopher Moore - up through A Dirty Job, then he became rather misogynistic and crude. Sad.
Jasper Fforde - Thursday Next series

Read The Flight of the Maidens & looking forward to reading a 2nd (Jane Gardam).

If you like mysteries:

Ellis Peters' Brother Cadfael series always charmed!

Porfiry Rostnikov series by Stuart M. Kaminsky have not disappointed.

John le Carre - wonderful.

I loved Sarah Stewart Taylor's books (Mysteries) w/Sweeney St. George. The author seems to be following another story line now and that's too bad. I miss Sweeney!

Of course Ken Follett is wonderful! Fall of Giants is fabulous.

One thing about prolific writers whose quality deteriorates as they age: it might not be just complacency. I heard a story on public radio recently about mystery writer Agatha Christie. Apparently her final novel was not much admired by her public. Not long ago someone did a textural analysis of the vocabulary of this novel compared to all her earlier books. It was markedly different. Apparently her mental abilities were declining. She was still doing the best she could.

Sad, really. But something to think about before getting annoyed at writers whose previous books have brought us great pleasure.

Rosefolly

I think I have read all of Anne Tyler's books and loved them, but the last one left me wondering if she had run out of good plots.
Barbara Kingsolver was a favorite also but have heard that her last one is not that interesting. I'll probably give that one a pass. Maybe someone here has read it and can give another opinion.

As a matter of fact, I liked The Lacuna better than some of Kingsolver's more recent books. She has become too EPA preachy for me. I loved The Bean Trees and Pigs in Heaven, but she has been down hill ever since for me.

Found this site recently and was looking through old posts and had to respond to this one. Marcia Muller's Sharon McCone series just keeps getting better. The stories and characters have evolved with the times, unlike a lot of other series where the characters seem to be stuck in a mental and physical time warp. Muller's characters grow through their experiences and life moves on for them in a realistic way.

Also the Jack Reacher stories by Lee Child and the Harry Dresden series by Jim Butcher.
Recently found Lisa Lutz with her Spellman family books. There are only 4 so far, but I hope there will be more.

Rosefolly, Do you think we change as well when we age, and our brains seek a different kind of book or reading? I use to read, when my children were young and needed so much of my time, Danielle Steele cover to cover. It filled the need to read when my mind and energy went in so many different directions. Now, I have no interest in them whatsoever...the last few I tried I couldn't read more than a couple of pages before becoming very impatient. But I can read history books and biographies, science based books for hours on end, which I had no hope of reading in those days.

However, I do remember getting so caught up in Trinity by Leon Uris, that my four year old came over to me, after saying my name several times, took the book out of my hands, and looked me straight in the face and said "Mom" in a strident tone. Yes, he is an avid reader to this day, some 36 years later!

Then there is the formerly prolific author for whose next in the series we've been impatiently waiting for 7 years - George R.R. Martin. About which Neil Gaiman famously said, GRRM "is not your #itch!"

No-one has mentioned J.K. Rowling yet! None of her 7 novels were a disappointment :0)

Here's hoping Rowling's pen is getting itchy!

I've read all of M.C. Beaton's Hamish Macbeth mysteries and will continue to read them even though every time I pick up a new one I think, "Hey, I've already read this!" I keep checking the date in the front to make sure it's new. But I love them, there is something comforting about these books.