Which iPod touch are you using? Because I have a 2g (yep, there still are people using them
) and with the last software it supports (can't remember which one is it) if you let the Wi-fi on it will consume your battery in no time. This didn't happen so quickly with previous iOS versions but I guess is the Apple way to tell you to upgrade, lol. Jokes aside, I think its quite normal for older devices, but not so sure how standard it is for newer ones.