I have heaps of batteries on lots of equipment. Some of it sits for months on end without starting. Without a doubt the worst battery brand for short life is Century. They have 12 to 18 months life in them and then they drop a cell. The best ones I have used are in house branded ones from western Batteries in Orange. I write the purchase dates on all my batteries and I bought a few in November 2011 and they are all still start spot on. These are mostly N70 size batteries starting diesel motors.
Don't let them sit flat and never leave a battery sitting on concrete.