Almot, maybe we are reading the OP's post a little differently -- I think she said that she has had the AGMs on a Batteryminder for a long while. I am not sure she has done a conditioning or equalizing charge.
The narrow issue is whether the pulse of the BatteryMinder is good or bad for AGMs. The broader issue is whether it is useful for any battery. Certainly, the manufacturer says that it is helpful for many kinds of batteries, and they cite a fair sampling of literature to back up that claim. But I don't know if it has been independently verified.
Meantime, my little black box is blinking away in my garage, and my ordinary group 31s are giving me great service. But that is just anecdotal. As they say, "the plural of anecdote is not data." I am not sure what that means, but it sounds profound.
