I'm not sure "average tour" makes sense. I've done a big variety.

This past weekend, I did a three day ride from Vancouver BC to Seattle WA. Earlier in August it was eight days cycling from Portland OR to West Glacier MT. I'm dreaming and scheming for at least a six month ride coming up and have done a ten month and twelve month trip in the past. In my current setup, it gets tough to take much more than a week at a time - so that is what the tours are at.

My guess is you'd be ready for a cross country trip in far less than 10-15 week long tours. When I look at things, there isn't as much difference as you'd think between a six day trip and a six month trip. A lot of the packing lists are similar and on that longer trip, you might be a little more inclined to mail something home or buy something along the way. I don't bring much different in amount of clothes. A six month trip might bring some additional visas and perhaps different climates, and would prepare to wear through tires and a few other things. However, not that much different.