Small Engines (Lawn Mowers, etc.): Battery Drained, cub cadet lawn, charging system

Question
I have small Cub Cadet lawn tractor that I have owned for 5 years.  I am on my 3rd battery.  I live in the South East and have roughly 290 hours on the mower.  It seems that I can no keep a batter in the mower.  Any idea if there is something draining the batter other normal use?  Should I remove the batter during the off season?

Answer
Hi Stu,

Sorry for my delay.  My ISP was down.

The charging system my be overcharging the battery, causing the electrolyte level to get low.  As long as you keep the water topped up to the correct level, the battery should be okay.  
When in storage,a battery will discharge over time. When allowed to stay in a discharged state, it will deteriorate, so it's best to trickle charge it once an month to fully charged.

Michael