is there anything needed to be done for a air compressor that is going to be sitting for awhile? i have a single stage 60 gallon i just bought and it is only going to be used for large air demand tools like my DA sander and paint gun. then i got a 20gallon to use for the impact and pumping up tires and whatever that isn't high demand. they both may sit for a few months before being turned on, do they require anything for this? i always empty the tank after im done but should i leave it open or close it?