The BatteryMinder float charger is meant to be left on the battery ALL THE TIME! That's what it's designed for! It constantly pulses the battery to ensure sulfation doesn't occur. Read up on them, you'll be surprised! I get 5 years or more out of my riding lawnmower 1 year batteries with no problems using one that's left connected to the battery any time the mower isn't in use - summer and winter.
They never boil any of the water out of the batteries. It sounds like Rupert isn't knowledgeable about "Float" chargers. They don't taper down when the battery's full, they stop charging and monitor the battery till it needs another boost.