Why does my palm pre wasty so much battery life when im sleeping?

so today i went to bed super late like around 5 in the morning and i woke up at 7 checked too see if i had anything new and the battery was still on green n when i went to bed it was like at 92% and like i said when i woke up at 7 it was still green, then when i woke up at 11:50 it was 77%? i had no txt messages or missed calls or emails. how can i conserve more battery, also does anyone no how to get free ringtones i tried myxer but it only streams it? and my computer cant use itunes plz help me!