Is too much charge time bad for your iPhone? [duplicate]

Nah. Electricity is PULLED to devices that use it, not PUSHED from the plug. The phone is smart enough to stop pulling when its battery is full.

EDIT: However, an adapter can provide incorrect voltage for a device. Don't take what I said there and wire your iphone power adapter to a 220 source, for instance. You can OVERDRIVE a device with too many volts, but you can't send it "too much" of the right voltage, because the amperage is a function of the device's draw. I know I just said that assuming that you understand the difference between volts and amps, but there it is; they're different.

No, leaving it charging overnight will not have any adverse effects. All you need to do with the iPhone's lithium battery is be sure to drain it once a month for longevity.

Read Apple's iPhone Battery page.

[Similar answer for Apple's lithium laptop batteries, iPad batteries, etc.]

Also see Apple's Lithium-Ion Batteries page for more info.

The answer is it's just like an laptop: If it's left plugged in all the time, then the battery WILL eventually die. So the answer is yes, it's OK to leave it plugged in, but not all the time.