What's a good percentage to charge your iphone 4s?

What's a good percentage to charge your iphone 4s?

100%?

Around 90% to avoid overcharging the battery, if you charge to 100% you risk overcharging the battery as the charger switches to a trickle charge to keep a constant voltage, there's no benefit to charge to 100% unless you really need the extra capacity of the battery.

ALL THE PERCENTAGE!