I unload at the end of each day, and the safest way to do that is to fire the gun in a safe direction (MUCH safer than screwing around with a ball puller over a full, live charge of powder). At the end of each day, the gun either goes into the back seat of the truck, or I bring it in each night (so some dirtbag doesn't steal it). With this comes changes in temperature and the possibility that condensation will wet the powder charge. I prefer a fresh load each day for this reason. And with only a single shot fired each day (maybe two on the days when "brown went down") there isn't really a lot of cleaning that needs to be done. A few quick swipes with some "moose juice" followed with a bore buttered patch, and you are good to go. Obviously, a thorough cleaning at the end of the weekend will be needed. Still waiting for the day when I can camp out and hunt for more than a weekend at a time...
PS: most states do consider an uncapped or unprimed ML unloaded and safe to transport. I suppose with a CCW permit (which I have) you could keep it half-cocked, locked, and ready to rock, but given the safety mechanisms on the old girls, I don't think it is too good an idea...