Good time to enter this convo....Age.....it does matter, just like size. (meaning it can be good or bad.)
First show: U2 at The Paradise Theater in Boston in December of 1980. They opened for a metal band. Lennon had been killed a few days prior.
It set the benchmark; not many shows I've seen since then have been able to reach that intensity. Seeing a great band on their first tour, immediately after one of their idols had died. The crowd was....sick. In a good way. By the time the headliner came on, everyone knew they had witnessed something extraordinary.
It's why I keep (after all these years) going to see local/unheralded bands. You never know when you might experience something....worth remembering forever.
And yes, U2 has had their very sucky moments, but after 23 years of following this band, they can still (sometimes) do justice to that little show in 1980.