I wondered the same thing when I did a tour over in Thailand a few months ago. Before I left I would bike as much as possible, maybe 4 times a week, mostly a 9 mile circiut then once a week I'd go for 3 or 4 hours. The most I rode was 34 miles. And thats in the last 5 years.

The first day of my tour was 90K, the second day was 144K, the third day was 70K and the fourth day was 127K, I'm not sure of the miles but all of those days we're more than 34 miles. I think the most I rode was 7 or 8 hours in a day, I'd stop stop to sight see when possible. I was carrying my own stuff but I did stay in hotels so did not have all that much stuff.

From my limited experiance, I'd say the key is to not let it become like a job, you're on vacation, you go to work inorder to go on vacaation not to contimue working. The last day of my trip I think it felt too much like work, and the bus to Bangkok just looked to good.

www.thailand.crazyguyonabike.com