Irex has some recommandations about it:
First usage and battery-life
To achieve the maximum battery-life it is required that you fully charge and use the battery for about five times. Over these first five charge-cycles you will see the battery-life improve. When you leave your device uncharged for a long period of time, it may again need a number of full charge cycles to get back to its old level. To keep the battery-life at its maximum level we recommend fully using and recharging the battery at least once a month.
Source:
http://www.irextechnologies.com/batteries