Being in a band means sharing most of your time with your co-workers. There could be good times and bad times because people change. The Beatles broke up because of that, suddenly they had different opinions about everything (the songs, the public image, politics, money, etc.).
They got together being teenagers, but when they became adults each one wanted something different.
The Rolling Stones had a lot low points:
Late 60s: Brian Jones was heavily on drugs, he was a drag for the band and they decided to fire him.
Late 70s: Keith got deeply into drugs. Mick took the financial and artistic direction of the band, while Keith got into problems with authorities wherever he went.
During the 80s: Mick wanted to make a solo career and Keith, recovered from his addictions, wanted to record another album and go on tour. They finally got together again under a business agreement and they have contact with each other as less as possible.
Aerosmith: They had a lot of break-ups and reunions.
Van Halen: Except the two Van Halen brothers, everybody is disposable.
Most of the time the problems are:
- Heavy use of drugs
- Disagreements about tour time vs. free time
- Disagreements about distribution of money
- Expectation of solo careers.
- Artistic disagreements.
If band members avoid these 5 issues, there is a chance that they can got together a long time.