How and when should I charge my battery for optimal long run battery life time?

[AC Question]

I have an S4 mini and I try to charge it when it's down to 2% and leaving it in the charger turned off until it is at 100%.
I have no idea if this is the best way to ensure long battery life time.

 

[Mihai HG]

It's best to not let it drain completely, try to charge them as often as possible, with lithium ion batteries it doesn't matter if you charge them many times, but if you let them drain they will degrade