Does leaving an Iphone plugged after it's been fully charged cause the battery to die fast?

Does leaving an Iphone plugged after it's been fully charged cause the battery to die fast? - 1

Added (1). Does it really cause the battery life over time?

No. There are lots of daft theories about this sort of thing. There was a fashion a few years ago for telling people that you shouldn't charge your phone too often or it would 'remember' that you charged it often and it would lose its charge more quickly. It was total nonsense but everyone believed it. You seldom if ever hear that mentioned now.

No. Like all lithium polymer rechargeable batteries, the charging circuitry very accurately measures the level of battery charge and then cuts the output down to a maintenance charge only when fully charged.

My five year old iPhone 4 is left on charge whenever I'm not using it but still works just fine on the original battery lasting all day between charges. My iPhone 5s gets the same treatment and now that it's almost a year old the battery still works like new.

It's probably a hangover from over ten years ago when many phones still used bulky Nickel Cadmium rechargeable batteries. NiCads suffer from something called memory effect which means they display a serious loss of performance if they are recharged before being fully drained. The later Nickel Metal Hydride (NiMH) and modern Lithium Polymer (LiPo) batteries do not suffer from memory effect.

No. IPhones don't overcharge.