Wow, it really nose dives when not plugged in. Use your phone less, Blanko.
I've heard you shouldn't charge a battery unless it's low on charge because it reduces the maximum charge the battery can hold. Makes sense because my phone's battery life sucks and I used to charge it and leave it plugged-in overnight.
I've heard the opposite about Li-ion batteries. You're not meant to leave them plugged in, because heat generation can kill them, but charging them early is supposed to prolong battery life.