How often should I recharge the Stanley FatMax when not in frequent use?

The manufacturer recommends recharging the battery at least every 30 days when the unit is not in frequent use. Additionally, recharge the unit fully after each use to prolong battery life. Frequent heavy discharges between recharges and overcharging will reduce battery life. Failure to keep the battery charged will cause permanent damage and poor jump-starting performance. (Page 9)