Propane and diesel is everywhere up here like others have said, so I don't think you will have any issues at all
However I don't think I would be looking to fill a propane tank when it gets to 1/2 empty, or when it's only 1/2 full ( grin)
But up and over here in the mountains looking for fuel when you get to a 1/2 tank when hauling a load like a RV is a good idea. Mountain passes will eat up fuel faster then a lot of people can believe, until it's too late.
When you get farther north fuel stops are plenty however they maybe closed, out of fuel or another issue could hamper your fuel plans.
Where we camp in south eastern BC there is a small town that is located in the mountains and I can't count the amount of times that there has been a power failures caused by trees causing downs power lines, vehical acedents causing power poles to break, and Forrest fires cause power failures.
By no means am I saying that that's going to happen on your trip, most likely not, however filling the top 1/2 of the tank also gives you a chance to stretch, check wheel bearing temps etc.
Have a blast on your trip
Soup