If it is 8 years old, and the voles didn't go underground to eat up any more, then you should have a burst of growth similar to what you got last year because most of the energy storage is underground. You just won't get any flowers since it takes above ground buds to produce those for most species.

Here's a blog post of my younger tree peonies getting girdled by voles, and right now, most of these are making a good recovery.

Here is a link that might be useful: My vole damage

Thank you, Steve - your blog is very well done. Thank you for that encouragement for my poor damaged tree peony. I will be patient and wait for it to regrow, watching out for any signs of the herbaceous root trying to sprout.
The loss of flowering is disappointing, but what made me so angry was all those years of steady growth just wasted. Grrr.

Believe me, it will be well protected every fall from now on with the same method that works with my shrub roses: a sheet of the dryer fabric softener "Bounce" (original scent seems best) tucked into the crown of a rose in late fall. This has always given me great protection from rodent damage over the winter on the roses. Apparently they find the fragrance impossible to live with. No, really, don't laugh - it does work. That scent is soooo strong, even I have a hard time with it, LOL - and it hangs on through the winter quite well. Cheap and effective protection.
I only wish I had thought to put a sheet in the tree peony but I never had voles up around that area before...but then, it was a terrifically hard winter that just passed and the amount of woody plants girdled during it is simply astounding.

At 8 years old I doubt if you'll have any problems with the herbaceous root trying to sprout, it's probably gone by now. I've heard the Bounce trick for keeping mice away from the garage, never even thought to try it on plants for voles! Wonder if it would deter deer from my daylilies.....

Laundry fragrance sheets sound like a good idea. I may apply that in my own situation. Once tree peonies have established for over 3 years in the ground, they are usually pretty good in terms of re-growing even if they are cut back every year.

They will simply behave like herbaceous peonies, but still need an above ground bud for flowers.

I don't know what kind of Peony it is but my grandmas poor Peony spent over 20 years with very little foliage or water because it was mowed for 20 years. I only found it because I was mowing and it dawned on me what it was. I had not seen it since I was a child playing on the swing. It now resides in my garden close to my door where I can keep a eye on it. Long story short they take a licking and keep on growing,

Most of my tree peonies are 46 years old. In that time they have been cut to the ground twice. Year before I cut down Taiyo, a nice red. this year she had 8 nice flowers. I usually dig in lots of compost and give them a bucket of cheleated (sp) iron.
I bought them from K-Mart for $1.69. They came in little cardboard boxes, bare root. I think I got my moneys worth.
Note, second spring for Taiyo after being cut down.

Thank you all for the reassurances. In going back through my records and photos I realized it is older than the 8 years I guessed at off-hand at first...more like 12 or 13. So I shall give it time to regrow and perhaps next year or the year after I will see its big shiny red blooms again. This one was a boxed cheapo, too - no name, just "tree peony" on the box. I remember being very excited when I found a small paper tag on the base of one stem that read "Shimanishiki" but that was a false clue as it has never, ever had a single stripe.
At least the voles left my Kinkaku alone so I will not be without any tree peony flowers at all this spring.