Again I say it depends on what you are doing.  If there is enough sight seeing, etc. to do for a month then stay the month - you save considerable.  Electric on our "hog" of a unit runs less than $100 almost everywhere.  That's two 15K AC's, washer and dryer, 2=TV's, 12 gallon water heater.  If the monthly saves us more than $150 (and usually does) then we pay that rate.  If we can't then we pay weekly rates - but I've only done that once at an "RV Resort".  And then we decided after two weeks to go somewhere else as it wasn't such a "resort" after all.