Before storing the batteries for a long period e.g. over a summer, it is best to discharge the batteries by plugging in the elements, setting them to say 2,3, or 4 until there is no heat being generated any more (or the red LED light is out on the battery packs), and then giving them a full charge (12 hours plus). If you let the batteries stay on the recharger after 12 hours (flashing LED), say another 6 to 12 hours, then the trickle current will nicely top of each cell within each pack. Then if you did nothing until a day or so before using them, that would be ok, but if you discharged/charged them in a similar fashion about once a month or two in between, that would be even better (but is not imperative!). Just make certain (before you use them each time) to discharge and recharge them the day or night before actual use (self discharge rate is somewhere between 1% to 2% daily).