when I first started riding I had a trek 7.3 and routinely rode 60-100 miles on it in charity rides. I did get thinner tires,and kept what I carried down to two bottles, underseat bag and a couple of protein bars and gu gels. Of course I was also riding primarily flat, had a support vehicle every 20-30 miles and had the whole day to do it. My best day was 100 miles in 7 1/2 hours of saddle time or 10 hours total. That worked out to about 13.5 mph so I say go for it, especially if you aren't going to worry about speed.

marni