Ditto on just letting it run. I've yet to set it at 80 and have it ever shut off!!
If you are parked in a hot state during summer the RV AC will never shut off and really never get as comfortable as a house does. And please ask around and talk to people who have added a second unit. All the ones I talked to said it didn't make that big of difference vs the cost.
These are RV's are nothing more than trucks with no insulation and TONS of windows. Just not conducive to air condition efficiently. Adding all the coverings does help but for me it was too much like a cave. I put the stuff up between the hours of 1 and 4 and then they came down. That's about all of darkness during the day I could take.
Lowering the awning on the side of the sun, leaving the covering on all the time on ALL the windows in the cab area and putting those pillow inserts on all the roof vents, seemed to make the biggest difference.