I have it turned off on my MacBook Pro, but on for my phone and iPad. my 4 year old macbook pro's battery is doing great, my iPad is still holding on (but it spends a lot of time unplugged or powered down), but my poor phone is hurting badly (4-6 hours of charge per day, claiming it's at 80% battery life).

my MacBook Pro still thinks its battery is awesome, even plugged in all the time.