Re: Cocking TAC-15
Twanger is totally correct in his advice on when and how to cock your crossbow.
The TAC15/15i has no real upper limit on how long you can leave it at full draw. Technically, it can be left in a full draw position for well over a dozen hours or more, but for safety reasons it's a good idea to practice the loading and unloading sequence often, so when you're in the woods, in a treestand, it can be accomplished with no glitches.
Many of us have found that in order to get the unloading sequence started, it often takes a few rocks of the crank handle with a slight upward pressure applied to the cable sled in order to get the crossbows string to move out of the fully loaded slot it sits in. This becomes easier with a little practice, but keep in mind the TAC15 is the only crossbow that I'm aware of that can be cranked back down to an unloaded position, so it's a great feature when hunting.