I was concerned about training myself before riding the 1st half of the TDT in 2006.  I am in my 50's and have been riding mountain and road bikes recreationally for only about 5 years.  I had never ridden a long ride or on consecutive days.  I began "training" for the TDT in July by increasing my once per week casual ride to riding 3 times per week at a faster pace.  My weekly mileage increased from about 10-15 miles per week to about 60 miles per week as late-November approached.  Prior to the TDT, I also rode one 45-mile ride and one 52-mile ride.  Those were my longest rides ever and I did just fine keeping up/hanging in with the riders on the TDT. Chris is right on target when he says that everyone gets stronger as the ride progresses.  We got stronger as a group and after the 1st week we were moving along pretty good and free of the first week's saddle sores. I will be doing the same general training regime for this year's TDT.  Can't wait to join in the fun again.