well i can only confirm my laptop.
it's been alive for er.. 8 months? and they say when u use a/c
power must take batt out, then must discharge fully b4 charging it
blah blah.. but bullocks to them i can't be bothered... so my batt
sits in the bay whether i'm plugged in or not (i'm usually plugged
in).
so i'm "mistreating" the battery, but still gives me 2hours ++++ b4
it dies, which is the same time it lasted me when it was brand new.
also depends on ur screen brightness, wat colours u use, whether u
play music, blah blah blah... 
