I see your point and understand what you are saying. The only thing I would counter with is that bands like Motorhead, Metallica, Testament, etc. will do this until they die, and as a fan I want that as long as the music is still great.
I understand that they can't compete with their old records but for me, there is a definite line separating bands from my youth who gave up and those who try to still bring it as best as they can. Like I said, Motorhead, Metallica, Testament, Anthrax, etc. come to mind. With that said though, Master of Puppets is my second favorite album of all time, only behind Appetite for Destruction from GnR.