Friel says "The purpose of tour training is to develop enough endurance and resiliencey to get back on the bike day
after day. Preparing to tour places a greater emphasis on weekly mileage, or more specifically, time in the saddle.."
The problem is that you will be spending so much of your time climbing. You will need to do some training climbs,
and you will need to reproduce the pedalling difficulty regularly, be it climbing in a higher than normal gear, a gym bike
at high resitance, or a spin bike with the brake screwed down til it hurts.