Do a forum search on geo method and you'll read more than you ever cared to about black tank cleaning and storage. But yes, you should clean, drain, and refill with some water and RV toilet chemical/geo method chemicals when stored.
2015 XLR Hyperlite 30HFS5 (mods being performed regularly)
2009 Salem LA 292fkds (gone)
Nights- ('12)23 ('13)23 ('14)15 ('15)31 ('16)27
2016 Ford Fusion Titanium (gulping gas again, camping support vehicle)
2014 Harley Davidson FLHX (XLR cargo)
2011 Ram 2500 CC 4X4 CTD, B&W Companion (toy hauler hauler)