The ctek is a great charger, and the answer to your original question is that if it's fully charged, then by all means take it off the charger. There are 7 levels on my charger, 6 is finished, and the 7th is just a maintenence level.

That all said, the charger can't rehab batteries forever. If you said it's dead again, then don't play with fire. You will depend on that battery and it will fail and leave you in a lurch somewhere. GO BUY A NEW BATTERY. Your best bet is probably Sam's Club or Costco, and maybe even Amazon, but ditch the bad battery now before you get in serious trouble on a Sunday evening when all the stores are closed and you're at the lake and the car won't start. Don't be a fool. Spend the money, get a new battery.

Oh, and use the ctek once a year on your new battery to keep it in good shape, and after any deep discharges. Like I changed my fuel filter the other day and you have to crank the battery a lot until the filter is full of fuel. That's a deep discharge.