I have one of those Turbostart agm red top that I purchased from Mancini's in 2010. I keep my Battery Tender on it ALL the time. I only drive my Cuda during Spring Summer and its up on jack stands during the Fall/Winter. The only draw is my quartz clock conversion. Once I get it in the garage, the Battery Tender is hooked up. This battery has been working great for me since new.
Interesting to read others experience with batteries. Got to be a quality issue with the failures that are mentioned here. Or you have to get a proprietary charger for certain manufacturer. A friend of mine has Odyssey batteries and he does not use an Odyssey charger. I do know that if you have agm, you do need to get a compatible agm maintainer.