Once per 24hr or longer period (determined by the GM based on the pacing of the story). It must be spent in an area of safety, such as an inn, where you can eat well, rest, and recover.
If you do watch, you cannot gain this benefit, as your Slumberwave pattern is typically interrupted or paranoid.
If the Full Rest is interrupted by any amount of Dangerous Activity you must begin it again.
At the end of a Full Rest, you gain the benefits:
-> You regain all spent Vitality Dice
-> Your Vitality maximum is restored
-> You regain all lost Vitality
-> 1 level of Exhausted is removed
-> You gain temp vitality equal to half your total level (rounded down).