I think if a band can stay together for a long period of time it is making it. It says a lot about a band / group. It's hard to get 3,4,5 musicians to always agree 100% on everything. Even more so the longer they are together.
To me selling out is when it becomes all about the money, and less about putting out good music. Please don't just toss an album out there with one damn good song and 7-8 other crappy songs for fill space.
"I was listening to music long before rock 'n roll." Bill Wyman