We get down into the low 50s almost every night here in Nor Cal and upper 90s to around a 100 or so during the day. Our humidity levels are very low, 2% to 10% every day. We don't have AC, just a swamp cooler and fans. Keeps the house at 72 during the day.
I kept a window open all the time to let the west-to-east breeze flow through the entire house. I only had to run the A/C during still days.
Now, in the Houston metro area, we're just coming out of a week-long 100+ heat wave. I can't live with the A/C above 70, just to filter out the humidity that seeps inside. If I were to set the A/C to 78, it would take a day just to cool the house down again.
Turning it up and down and up and down would be less efficient than just letting it keep a steady pace of coolness.
-PJ