I did well right up to the late 40's, but everything started slowing down around 47 and has not stopped.
At 50, I do feel as though gay life has passed me by. Gay life glorifies the young. The old (over 50) are just...old...
As others have said, I am definitely much wiser than I was at 25. I wouldn't trade that part for anything.
I will say that the fact that the sex drive has slowed down a bit is actually not all that terrible...I was SO horny when I was younger, now it's slowed down to what I would consider "normal".
One way to answer the OP's OQ might be: the first time "Mr. Happy" failed to respond when called upon. That was the first day I felt the "icy finger" down my neck...
One very liberating thing about being 50 is that, once you're too old to care, you can be fairly outrageous and nobody says anything. There's no compelling reason to try to keep up any more; if you admit your age and physical shortcomings, you can get away with wearing hawaiian shirts, sandals to the bar (a definite no-no when I was young), just meeting people for the hell of it instead of "hoping to get laid"....You are far enough away from the "young" generation that you think totally differently than they do---AND IT'S OK. When you're in your 30's and the "younger crowd" is just a little more hip, a little more "now", and you feel yours beginning to slip a little---that's MUCH worse than when you're 50, you KNOW it's slipped, and you accept it and start to just have fun.
I will repeat: I wouldn't trade the wisdom, even for the younger body and harder dick. Not even for that.