I always cock the crossbow immediately after I get into my tree-stand (or in the ground blind.)
It stays cocked until I'm ready to stop hunting.
can be let-down without firing it.
Note: This is accomplished without pulling the trigger.
The DvD video that comes with it shows you how. It's pretty easy.
I have never left it cocked for more than 4 hours, and don't know what the upper time limit is.