another very important point is that a brand new loaded up touring bike is going to loosen up spokes etc etc after a week or two etc of riding, so it's entirely in your and your bikes best interest to get spoke tensions checked after doing a bunch of pre trip loaded riding.
this is pretty basic and will help reduce the chance of mechanical problems into your trip.
If the person putting your bike together knows what he's doing (and that's never guaranteed), tell him what you're doing and he can go over the wheels and make sure they're built correctly (tension and stress-relief). The REI on the other side of the country did that with my replacement bike after day one (cracked frame), and the wheels needed only two light touch-ups crossing the country.
FWIW, if you can make it to Missoula, MT, Hellgate Cyclery was a block and a half away from Adventure Cycling's HQ and did a great job touching up my wheels at minimal cost. Recommended.