depends on use and geography. I use mine regularly, it stays turned on. I have a drain plumbed out of the bottom and drain at least daily. More often if I'm using it constantly during a day of sandblasting or painting. Can't have any water in the system. Just a open till dry/close. Once a week, I turn the compressor off and completely drain tank and all valves at each drop. I drain and replace oil about every 6 mos. inspect the fan belt monthly. I have a 5hp IR 80 gal compressor. The higher the humidity and use, the more important this practice is. I'm in a high humidity area, so I practice it regularly.
