Last SR-71 pilot I had dinner with was my age at the time - 40 years old when he lost an engine and landed at my base.. A student of mine 5 years younger flew the beast over Libya in 1986 ( El Dorado Canyon, I believe - Brian Shul), so would have been in late 30's.
Only the shuttle guys were lots older than the early days of NASA. My roomie flew first hop back in '87 or '88, and would have been in his late forties, but had been selected about 8 years earlier. He then flew on the MIR about 8 years after that, so figure it out.
Make no mistake, experience counts. However, that experience must involve a few instances of abnormal systems or situations. Our profession exposed us to many while we were very young, and they turned the keys over to us when we were 22 or 23 years old. Think about a troop in his late 20's flying a Raptor or Lightning that costs about as much as many airliners.