I don't have anything in my own limited collection that is older than 3 years. That's not by design but by usage. I try to keep them at a moderate temperature and the oldest ones are fine. On the other hand, my wife has some older perfumes, including some that she probably got 13-15 years ago. She reports that she's still happy with them and one or another of them will periodically appear in her regular rotation. I can't complain about them either!
I did buy a flacon of Vintage Tabarome before it went back into the cellar so I'll be running my own experiment with that for a while.