I have tulip bulbs next to my house which were planted by the previous owner, i.e. exactly in the 1980s. The leaves come up every year, there might have been a small flower, too, but I wasn't paying attention because I used that space as a dog pen. So I'd say it's not quite uncommon for tulips to last that long, as well as produce an occassional bloom.

I also have some very old ones - in tulip years - that I planted, I think more than ten years ago, that come up and bloom every spring! They are almost black but I did not record what variety. Might be Queen of the Night or Greuze. They are in a totally neglected, never watered or weeded, part-shade spot. I am truly amazed by this.

Last year, an area of yard that was a dog pen has been opened up and the fencing for the dogs moved... this spring, bulbs are growing that the home owner's Mother planted as long ago as 20 years! There are Daffodils, Oriental Poppies, and what I think may be Lycoris Squamigera! The Poppies actualy bloomed!

I plan to move the bulbs once the foliage begins to die back a bit... I'm sure they need to be divided... doing this may revive them somewhat, and next year they may even bloom better!