If i have helped at all a click on the white star below would be nice thanks.
Slow charging is good to preserve the baterry. If you must recharge the battery fast, use the Nokia´s recharger, but if you leave the cell recharging the entire night, use de slowest as possible recharging mode. It´ll recharge the entire battery anyway and will preserve it for more and more future recharging.
Other tip: use the battery to the extreme end, until the GOODBAY message and recharge it for more 30 minutes, after the full bettery icon on display. It´ll preserve the baterry´s life for much more time and rechargings.
@Artmos your suggestions may be valid for Li-Ion batteries, but they are not suggested for Li-Polymer. For example, using a Li-Po battery to the extreme end will definitely shorten it's life.