I've got an 85amp leisure battery - I charge it once a week - but I wired in a split charger which is excellent. It always seems to be somewhere between 12.3 and 13.0volts. At the weekend I give it a charge with my digital-all-singing-all-dancing-but-bloody-expensive-battery-conditioning charger
My previous battery was lasting about two days max, and I think constant charging with a standard charger reduced it's capacity and life
Dave