for nokia's batteries hor, i notice that if you don let the
battery die first before you charge it, it will die faster.
i mean not the first time when you bought the phone.
example like say if you still got 6 bars left and you think it wont
last you throughout the day and you decide to charge it to full or
you overcharged it( meaning the battery is already full but you
forgot to unplug it from the charger), & you keep doing this
regularly, sooner or later, you will find that your battery life
actually gets shorter.
a few of my friends using nokia also say the same thing.
donno for others.
and when the battery got so bad, that the back part of it
surface up, you will find that whenever you make a phone call, or
recieving one, the battery will shut the phone off in
2-3mins.
those were my experiences in the past, when non-colour phone are
still popular.
nowadays, batteries don really shut phone off but will die off
faster than when it's first bought.
when you just bought, maybe it can last 6-8hrs, but after bad
timing of charging, it becomes 4-5hrs.