Sure batteries will discharge while sitting but like most everything else, you get what you pay for. IMO optima batteries are junk, tried a red top back around 2006 in my Chevelle and it didn't make a month before failing to turn over my engine when I was called to the lanes and it was charged with the correct AGM charger. Went back to the same AC Delco that I've been using since the early 90's with out issue or failure and I've never used a battery tender nor remove the battery(s) from my car in the off season. Same batteries in my Firebird since buying it and I will have no problem starting the engine in late February when I take it out of the trailer to ready it for the season. BTW, same batteries in my tow vehicle too.
