Personally, i would consider a vent cover like maxxair if you do not already have one and use the vent fans to help it air out and keep the humidity down. Unfortunately, i am new myself and do not know the specifics of "should it always be on or do you turn it on x # of days before a trip etc". Hopefully some body can fill in that gap. Do you pay for elec usage? Or just a flat fee that includes electric? I have heard of some using the heat/ ac to help control humidity and makes items last longer...
Darn sure wish i had electric at storage site for and afforable price
2011 Heritage Glenn 312QBUD
2011 F-350 SRW Lariat FX4
2014 Sandpiper 365SAQB