They can be stable for a few years at a time if there's lots of food, water, and decent weather, no injuries or major stressors. So yeah, boss monkeys don't stay that way forever, and it requires lots of work maintaining health and social relationships. The physical challenges are a function of pure physicality, there's no monkey jiu jitsu, it's all rage flailing - the fights are probably a lot less work overall then the socializing.