Keep all lead-acid batteries charged up. During discharge, or kept at low charge, a process called sulfation occurs. Over time, this cannot be reversed and the plates gradually degrade until the battery won't hold a charge. Sulfation can be avoided if the battery is fully charged after each discharge, and held on a float charge.
For best life, lead-acid batteries should be fully charged after each use, and held on a float charge until the next use. Your good-qaulity charger may prove to be a better investment than constantly replacing a battery that loses life and is improperly charged - good leisure batteries are not cheap! These links give more information. HTH
http://batteryuniversity.com/learn/a...d_acid_battery
https://en.wikipedia.org/wiki/Lead–acid_battery