I'd have to ask the question:why wouldn't you train for a cross country ride? It seems like a lot of folks equate training with some onerous exercise that is as much fun as going to the dentist. I make the assumption, maybe erroneously, that someone contemplating a cross country bike tour actually likes to ride bikes. We take long rides whenever we can, not because we are "training", but because we enjoy riding. Training can be fun!

My wife and I ride year around, but put a little more emphasis on hills as the start date for a tour gets closer. On our trip across the U.S. we started the second day with a 4,000' climb over a 4,500' mountain pass. That was followed by another mountain pass the next day. On that same trip we averaged over 50 miles a day on loaded bikes for 74 consecutive days. Being in good shape allowed us to enjoy the riding, even the 4,000 foot climbs and 80 mile days. Riding across British Columbia into Alberta last summer was almost constant climbing. Did we train for that one-- #@$% yes!

Heck, on a ride the other day, my wife said, "maybe we should do some hill work today." Ugh!

IMO-I also don't believe you can ride into shape with out factoring in very light days or complete rest days. Sure your butt gets used to the saddle and the body accommodates for some of the stresses placed on it; but if you get into a jam there may not be a reserve to draw from. Most exercise training regimes use the concept of stress and recovery to build up strength and endurance. Look at many of the published training regimes for doing a century. A lot of them are based on an 8 to 10 week training schedule, and that is only 100 miles for one day.

Having said that, it is a personal choice, and there really is no right or wrong way--only what works for the individual.