When should a band call it quits?

As a sports fan, I think of this situation as it applies in sports and it happens often. The situation is when should a sports star retire? They love the game and sometimes they play beyond their prime and they tarnish their record by becoming a joke. Back in the 80's this wasn't that common in metal, but now it is as many bands from the 80's embark on comebacks, reunions or whatever they want to call them. I think about some of these bands who do tours every summer and I am reminded of some words from one of my favorite Halloween specials. In the Peanuts Halloween special Lucy is asked where Linus is and she says something to the extent of "He's out in the pumpkin patch making his year fool of himself." So my question is are some of these bands who don't do albums, but just tour each summer just out there making their yearly fools of themselves? Or are the people who pay good money to see them the fools? I don't go to that many shows so I have not been to any of shows although I have thought about going to a few. This topic does tie in with one I wrote about hasbeen tours back in maybe July. To get back to the heading, when should a band call it quits? A number of these guys are not putting out albums so they are just touring. However someone like Cinderella aren't doing albums yet they are supposed to be really good live and they have the same line-up that did most of their tours in their heyday. While other bands like LA Guns and the Bulletboys are doing albums that get poor reviews and these bands have just one or two members from their prime days. I am sure the band's answer is they stop when the people stop coming to see them, but I think that's when they started doing package tours with the hopes that four bands will bring enough of a crowd for it to be worth their while. My feeling is a band shouldn't be doing continual tours if they are not doing albums. I know that's not written down anywhere, but that's how I feel. Yet I see pictures from these shows and it's a lot of guys my age or even older going to see them. Virtually no kids unless it's the kids of people from my age who have somehow gotten their kids into 80's metal bands. A lot of the bands that are embarrassing now are bands that have been embarrassing for years or don't have that much musical talent to begin with.