forkbeard says:
what about the elvish trance?
and watches?
Despite the literal reading of the rules, I have always been happy to say that a 4-hour elvish trance can count as a long rest. In fact, I suspect we've already played it that way in this game. I see no reason to change that. That being the case, whatever we decide upon for long rests in general would apply to elvish trances used as long rests...that is to say, while an elf can go into a trance at any time, only one trance can count as a long rest in the given period.
I'm not sure what you mean by "watches," though...is there a rule or ruling needed about watches?