I have this MBP 2.53ghz for about 5 mos. i read that the battery can last up to 7 hrs other says around 4 hrs. But on my laptop, its just 2 hrs after getting 100% charge. i just did facebook, email and skype w/ video using wifi internet. Im also running in 30-40% display. Is it time for me to send this back to the store for replacement since it still under warranty? i already did battery calibration this month 1 time only. installing the snow leopard can also solve my problem?