42 miles is very long, typically the pioneers didn't go more than 15-25 a day, but I guess they were walking and sparing thier animals. I go about 6 and it takes a couple hours which also includes tacking up.
As far as drinking out of a river or stream, can't wait to see th responses on that. I am an agriculture major and I would consider it unsafe. Some rivers and streams might be ok, but I wouldn't risk it. There are things that you can't see and I would use that water as a last resport. Pesticide and fertilizer runoff from farmers, industrial chemical runoff, animals feces that could contain pathogens such as gerardia and coccidia are just to name a few things that might be found in water that looks relatively safe. These things can travel a long ways so even if you don't immediately see the effects, (dead fish, garbage) doesn't mean they aren't there. Even the lowly person who has a yard up the way who put fertilizer on their grass or chemicals to kill the weeds on the shore could contribute to the pollution. I would google your area and see what the reports are. For myself, if I was to go on a long ride, I would find a way to carry my own water, or just wait until I got back home.