In my area most run their sprinklers too often and not enough...many people are running twice a day cycles never soaking the ground.
Also, the length certainly depends on the GPM of your sprinklers. I normally use 4 GPM for the full circles and 2 for 1/2 etc..with this combo, I run 45 minutes for each rotor zone BUT only 15 minutes at a time with a min of 30 mins between cycles (some controllers allow this cycle/soak automatically). This is 3 times a week max to get a good soaking less often. This gives me about 1 inch/week.
I also notice that not many use rain sensors...it has been raining here for a week and I still see peoples sprinklers going. A $30 sensor would stop it.