If I haven't flown in more than a week, I'll charge everything the night before I plan to go fly. That said, I still check battery voltage before EVERY flight, with a loaded meter, especially when I've brought several planes out. Case in point, at our last fly-in, one of our most experienced pilots flew his 1/4 D-VII after a full charge. Landed, flew another plane, walked around, visited, etc, flew the second plane again, then flew the D-VII about three hours after the first flight. Made it around the pattern once, lost everything, crashed. Cause? He didn't check his battery voltage before the second flight, and had left his Rx on after the 1st flight, and had a semi-bad servo that drained the battery between flights.

I also cycled my NiCd's once a month if I'm using them regularly, or after about 15 recharges, regardless of how little they were used each charge. The newer batteries are less prone to developing a "memory", but I believe it helps make them last longer and hold a fuller charge to occasionally discharge them and then recharge fully. I've pretty much moved to all NiMH, and am exploring Lithium batteries, but can't justify the cost for the advantages yet.