OK, so I'm rigging a parallel setup for charging three 12V batteries. Two full-size deep cycle and one smaller (motorcycle-sized but deep cycle) that's for my fish finder. I have a 1.25-amp charger. YES, I understand that it will take a great deal longer to charge with such a low-amp charger, but I will very rarely need to charge even two of them at the same time, much less three. This is mainly for ease of the maintain-charge.

If one depleted (say to 80% battery) is hooked up while the other two are at maintenance, what will the drawback be? Minor decreased battery life? I could unhook the at-charge ones to charge the depleted one and then parallel them all up for maintenance; is it worth it?