I think it depends on where you're at and what the temperature is.
I hunted the Baja a couple years ago and it was hot as hell during the day and not much movement so we'd move during the heat of the day to get to different vantage points and glass the first few hours in the morning and in the evening.
We shot a sheep in AZ about 15 years ago in December on a nice cool day. I found them about an hour after first light and proceeded to have a couple of meals on the hill while my buddy with the rifle made his way over to take a look at them. Finally made it to me a bit after lunch. The group of sheep was around 25 head and the majority of them were up and about the entire time. A good chunk of the time I got to watch two rams butt heads. Kind of interesting to see them smack each other and then a second or so later hear the noise. Kind of cool.
I spent five days scouting in AZ 12B the week after Labor Day. It was REALLY hot, but I did see sheep moving from first light until sunset. They were all close to water, either springs or the river, and the activity was probably enhanced by the rut (really cool to see)! A typical day for undisturbed sheep (glassing from a high vantage at long distance) seemed roughly like: up to feed an hour or two after 1st light, feed and wander for 2-3 hours then bed down in the shade, a trip to water around 11 or noon then either more feeding or back to bed, up to feed again around 3-4 and up until dark or bed just before. There was some variation of course, but this seemed like the typical program. If I was't seeing them up and about, I could usually find them in the shade of a big boulder or cliff overhang.
That's my limited data for now... will try to report again after more scouting, now that it's starting to cool off!