[Max Cow Disease]

I've read various tales about this on the web but I've never really found out for sure; is it possible to charge devices like tablets or phones for "too long"? I've always been fairly OCD about disconnecting my Nexus 7/iPhone when it reaches a full charge because I've heard rumours that it can damage the battery otherwise. However, I inevitably forget from time to time, and last night the Nexus was plugged in all night after being fully charged.

I'd assume that the more modern devices include some sort of disconnect circuit once the device is charged, but what are CP's surely insightful thoughts on this matter?