I prefer bands (and solo artists) who continue to create new music and diversify to those who turn into “relic” acts...still performing the same material over several decades. I’m not going to mention any names because I’m sure we all know which, bands in particular, fall into that category. The secret to knowing when to retire is something certain people can’t seem to grasp, probably because of the money which can be generated by live performance tours. Unless they are promoting some new material along with 30 and 40 year old hits I can’t see the value of listening to deteriorating voices. The voice does not stay the same throughout an artist’s career, it’s range and strength wanes, and new material will take these changes into account and it will be more easily performed than the old music which was created for younger, stronger, more pliable voices. It may disappoint some fans when the new music sounds like a move away from the earlier stuff, but it is inevitable, because anything else would be trying to replicate and not create or evolve.

I understand what you're getting at, and have pondered about this before. I think some of it is just due to age and experience. I suspect most young and inexperienced people tend to be more creative than older experienced folks. Not that older folks are not creative, but I think it isn't the same kind of creativity.

They should do whatever they want to do. Just because you like or don't like it really doesn't matter. It is whether they like it that matters. Most musicians play for themselves, not for you. If you want to go along for the ride fine, if not, that is fine too.