I think it's possible to get burned out. My brother in law supposedly is burned out, even though he's only done 3 of them. I think cruising for him is a type of vacation he doesn't prefer. He's uncomfortable in certain settings, such as a formal dinner. He doesn't like tipping anybody. He doesn't like gambling. He doesn't like structured dinner times, etc.
He prefers to have no rules, and as such cruising doesn't suit him well.