I went to see Green Day at Old TRafford in June, slink. There were people a lot older than me there and I'm 38. Get yersen' along. You're never too old.....
I'm in my fifties and when I go to concerts find that there are many older than me. Remember people brought up on the Beatles, Stones, Hendrix etc. are now in their sixties. My Mum went to watch her hero Morrissey when she was in her 70s
My ex mother in law is 71 and goes to more gigs than I do- she's just come back form a heavy metal festival and I think that if you're happy in your envirnment then it really doesn't matter:)