That's a really good question and I think it depends on a bunch of stuff, including your seat, peg options, personal health and so on. Here are my 2 cents, having been thrown out of the nest several times last year. Early last spring I went from 3-4 hour rides/day with breaks, to an 8-hour group ride across some slab but mostly twisty biways into WV (thank you again Pokey!). I was in full gear on a stock V-Strom 650 seat, and the group was kind enough to take short breaks every 90 minutes. I was in marginal shape and suffered (still do) from a bad neck and lower back, so the day was rough at times, but I hung in there and made it work. I was a wet noodle when we arrived and made full use of stretching, ibuprofin and whiskey to ease the pain :-P. That night, I got some excellent advice. Stand on the pegs from time to time if your bike allows it. Be in decent shape and stretch before, during and after a ride. Ibuprofin helps a little. Flapping your arms helps to avoid "cricks in the neck and shoulders". Keep shifting positions during the ride to avoid over-stressing any one group of muscles or joints. Stay hydrated and fueled with food to avoid cramps. The next 8-hour day went much easier because I took their advice, plus I had worked out "riding muscles" the day before, and the following 8-hour ride back was even more doable for the same reasons, and a couple long rides later in the season were similar, though I'm pretty sure I'll upgrade the stock seat before spring, probably with a Corbin. Anyway, 10 hours is pretty long for me, even in the car. I did a 12-hour car trip in icy snow from Columbus to DC two years ago and it sucked a lot, but I got it done. I imagine it would be similar to a 10-hour day on interesting roads on a motorcycle, and as such, I'd personally probably break the trip up just to keep the enjoyment level up and the risk level down.