I think it ultimately depends on what your motivation for playing is. I love playing bass and I enjoy the odd gig, but most of all I love the process of coming up with and developing new ideas. I'm 53, and for me, this motivation remains undimmed by the years.
Covers bands have their place and can be fun to listen to, although personally I'd rather they tried to put some kind of twist on the songs that they play, rather than mindlessly regurgitate the original version verbatim.
Tribute bands though? Seems a little too close to musical theatre for my tastes, all that dressing up as Bono or some other silly billy. It's not exactly rock n roll, is it? In fact it all seems pretty naff. But lots of people seem to like it, so what do I know? The public wants what the public gets, right?