For many years SMB used Lifeline AGM batteries. Bob was the contact person at Lifeline ( http://www.lifelinebatteries.com/contact.php
), and he was always very helpful. While there have been concerns about overcharging for years, Bob indicated that he had not seen their batteries damaged by overcharging, but rather by undercharging. This makes sense because the starting battery(s) are subject to the same voltage from the alternator that the house battery(s) are. This is also why SMB recommends solar panels and/or connecting to shore power to fully charge the house battery(s), as the alternator will only charge the house battery(s) to about 90% capacity.
Lifeline's original case design was replaced several years ago with a stronger one to eliminate the case "bulging" that was visible to a certain degree on a new battery.
SMB started using East Penn Deka AGM batteries last year because of the nationwide warranty service available, and for the fact that they enabled SMB to hold prices on the batteries (lead prices were skyrocketing).
I hope this helps.