Best answer as chosen by user Papa-n-Lola: My advice...

...is to charge the phone/battery when it gets down to 25%, which can be daily depending on your average usage. Typically, I charge my phone every night because I am a power user. Sometimes I have to charge more than once a day when I use my phone more than normal.

As I understand, modern batteries and chargers stop charging when the battery reaches full capacity and there is no harm leaving it plugged in overnight. Granted, I wouldn't leave a a charger plugged into the phone for days at a time. I believe that there are many misconceptions out there about charging due to the old NiCad batteries and building up charging "memories" or overcharging/overheating as a result.

I am not claiming to be an expert, just offering my "educated" opinion based on my knowledge and experience of such items. Take it for what it is worth.