Till you learn your batteries and assuming you have a good 3-stage charger/converter every month... If you have a magnetek 6300 Every day.
The level when filled and charged should be about 1/8 to 1/4 inch below teh bottom of the filler tube, DO NOT fill to the top and do not allow the plates to be exposed.. NOTE: You do not need to refill so long as there is at least 1/8 to 1/4 inch on top of the plates... But when you fill 1/4 to 1/8" below the bottom of the tube. This leaves enough space for the battery to "Breathe" .