I have a UFO from around 1982 or 83- but it was finished at that time. The reason it's a UFO now is that about 15 years ago I dug it out to show in an art gallery and realized that it had been damaged while in storage and needed to be repaired. The gallery wanted to show it anyway, so after the show I was going to repair it, but that never happened. It's been sitting, waiting to be repaired ever since...
The next oldest is from 2017- so not too bad, but it needs more work than what I want to put into it at the moment, so may or may not finish it. Counting those two, I've got a total of 20 UFOs (down from a high of 40 a couple of years ago).
Except for the one needing repair, all of my UFOs are in various stages of being pieced as I would rather quilt than piece, so once they get to the point where they are ready to be quilted, they tend to get done.
It may be years, but most of my current crop of UFOs will eventually get done...probably.....
Rob