Ive never cycled for 10 hours, but 4-5 is quite common. One thing i noticed yesterday after cycling the disused trainline Brampton Valley Way and back, is that with next to no junctions, no shoulderchecking and no hills meant a very static position and getting more achey than normal, especially in my neck.
I change my hand positions a lot (on flatbar), resting on palms, holding with fingers, sometimes playing imaginary piano on the brake levers to keep the tendons moving seems to reduce the problems there.
I also make sure my shoes are quite loose so they dont get too tight and numb when they swell a little.