I think that it all depends on the PM. If your PM understands that it is OK to do nothing sometimes, it is completely different story than PM who expects some work every day.

It nails down my problem with most of the methodologies: they all do depend on people involved, yet there is very little talk about the right attitudes.

(FYI, according to Harvard Business Review and similar publications, the direct management is one of the main reasons why people decide to leave)

(BTW, why you downvoted him?)