I flew (MPA) until I was (compulsory) retired at age 65 and didn't feel any different to when I was 40.
Although I can't fly the real thing any more, I am still teaching and examining in the simulator and still hold a Class One medical without any restrictions (apart from having to carry a spare pair of specs).
I agree with a previous poster that some pilots that I have met have been knackered at 45!