Of course, after bed time, the inside temp doesn't have to be 70, but would be nice around 50.
That is about exactly how we keep ours when boondocking in temps down to 0*. We usually turn the temp down to about 55 when traveling, but bump it back up if we stop for more than a few minutes. By the time we can make a sandwich, temps are already back up to 70.
Summer time, we are good up to about 80* during the day as we use the fantastic fan to create a breeze. Above that and we start looking for either higher elevations for cooler temps or campgrounds with hookups so we can run the AC. Have camped in temps up to 100+* and didn't have any problems keeping the camper near 70*. Not surprising since the AC is 13,000 BTU. For comparison, my 35' wheel only had a 15,000 BTU unit and it stayed cool too.
And while my camper is reasonably well built, it only has 1" walls, single pain glass. There are better built campers with much better insulation which would do even better.