one month shouldn't really kill your batteries since you turned the disconnect switch to OFF. I use the RAID bug bombs that you place in a cup with a little water because they don't leave any film or smell and it also gives you some time to get out. I totally dry out fresh/gray/black water tanks and water heater by opening all drain valves over night. Also don't forget to empty the inline water filter if you have one. AS for the black tank I empty and clean and libricate the toilet valve. Then flush the tank several times with pinesol or the like. The next day I close all valves so critters don't crawl in and make a home. For one month you choose on whether to put the feet down or not.