so yeah .. i have this SIM card for 8 years already and i use it on my N900.
but my friend also got a old SIM card on his NoKIA as well. but then he got a brand new SIM card from his friend that works for AT&t
and he claims that his battery life have improved at least 20% and up

he is doing the same phone usage with the new card as what he was doing with the old one.

anyways . i just wanted to know if replacing my phone with a new card will really improved the battery life or not.

btw. i highly doubt that my friend is lying to me because we are good buddies