I have charged the battery once [6 months ago] since I ran the car at the last Dat Nats last year. I started the car 2 weekends ago to move it, no problems. From memory the Battery tech at Absorbed advised i should put the battery on charge every 3 months or so, just to keep it topped up though.

I recommend giving the supplier a call to determine which battery would be best for your application. The GT12-18HR just runs the ignition on my application, so you may need the larger versions available to suit running headlights and other accessories and the like.