I guess I should have put this in my first post too. I am a backpacker also and one aspect of hiking I have come to realize is when I get the chance to go I go for some good miles in rough terrain - upwards of 10 miles/day. Not being in shape when I go means I over-work myself and when I get back I am in real rough shape. The last big trip I went on we did 13 miles in one day and dropped 3000ft in elevation. We ended up hitch-hiking out the next day because I tore up both legs and couldn't walk any more.
My point is - in riding it is my goal to build my legs up and stay there. I know biking and hiking are two vastly different activities, but working my legs routinely is better than not and I find riding is a lot easier, and enjoyable, for me to do and stay focused on than walking around the neighborhoods. I haven't over-worked myself on the bike like I have on a hike yet, and I hope I don't, but I want to find a balance and progression of time/miles and amount of exercise to get where I need to be, I guess I can't quite define it other than that.
As to the touring - the guy I'm wanting to ride with will do anywhere from 50 to 125+ miles a day, depending on terrain. So I suppose that is a good goal to hit too.