I discharge my batteries once a month if I haven't been flying.

As mentioned above, I have a timer set to a five-plug powerstrip that goes on for about 75 minutes every day. I keep my flightbox 12v, two planes and one transmitter on this all week so I can be ready at a moment's notice (I live a mile away from our field).

I played around with the time until I found what seemed an optimum daily charge to keep my 9C at a steady 10.8v readout.

I then added what I think is a damned clever idea. I have one of those timers with the pegs for on and off. I set it to come on at 3:00PM and go off at 4:15 PM, and I took just an "off" peg and set it in the noon position. Now, when I come home from the field I turn the timer "on" at 8:00PM and it charges everythng for 16 hours, then switches off the next day, but still comes on for the once daily charge all on it's own thereafter. Slick.