if you are talking about running a deep cycle battery, they will survive a "cycling from fully charged to fully discharged" without any problem. But if you don't "cycle " them they will loose their ability to cycle. The only place for that type of battery is if you are running an inverter battery bank or a trolling motor. If you ever go to a bass tournament, you'll see the pro's running the trolling motors on the trailer to run teh batteries all the way dead before recharging them. I find deep cycle batteries generally don't have enough cranking amps to spin a motor over fast enough to start(especially with EFI) on a cold day. I pull deep cycle's out of boats on a regular basis and replace them with marine starting batteries. They make a "dual purpose" starting/deep cycle battery, but they generally do neither job well and are just a waste of money. I've had to educate hte West Marine Salesmen around here on more than one occasion about the proper battery to sell a customer. If you have a battery going dead, figure out whats killing it(probably your stereo) or if the battery is bad. Worse comes to worse, install a battery cut off switch so you can cut all drains off your battery when its not in use. They make those for boats adn race cars, make sure you get one that will handle the amps, like anything, they make cheap ones and good ones