I'm 40 years old and still going to see concerts. I'm seeing Judas Priest and Slayer next month. I also saw Ozzy Last August when he was 70, and had a great time.
If you like the band, and you're into their music, you have nothing to lose. Its going to cost you, what, like $40 or less with groupon. And what's the alternative, sitting at home watching TV or something like that? So you go, have a few drinks, rock out to some music you love, I see no downside.
Worst case you have a just OK time, but at least you can say you took the opportunity when you had the chance.