A few itouch questions!!!?

hi i have 2 question about the itouch. the first one is how do i conserve power? i use it for like 3 hrs and the power is GONE. the second one is i know that if i turn off wifi the power will be saved. so i was wondering if i turned off the wifi will i have to reenter the pword when i turn the wifi back on? please give helpful answers the best answer will get the most amount of pts possible.