I've never done anything that dramatic, but on my tours across michigan, I've broken several derailers, both front and rear. If you plan to do a lot of shifting on acount of it being mountainous it could happen. I would carry an extra front and rear derailer, and it would also be wise to carry a couple cables to go with them because the old ones will probably get frayed making them impossible to reuse. Plus a new chain and several masterlinks would be a very good idea.

The other thing I would do is replace your entire drive train just before the trip if its not almost brand new. In my experience the derailers break most often, but everything else can and sometimes does break.