I want to charge my iPod 4G over night but I'm actually afraid it will reduce battery life...

There has actually been a lot of debate about this question. I think it's completely fine! I have an iPhone and I plug it in at whatever percentage it's at and before I go to bed. The next morning, I unplug it and it seems to have no affect internally to the battery levels etc. My main priority is that it gets charged so that's all that really matters so long as it doesn't damage the battery which it doesn't. :)

There has actually been a lot of debate about this question. I think it's completely fine! I have an iPhone and I plug it in at whatever percentage it's at and before I go to bed. The next morning, I unplug it and it seems to have no affect internally to the battery levels etc. My main priority is that it gets charged so that's all that really matters so long as it doesn't damage the battery which it doesn't. :)

I wouldn't charge it all the time, but it's fine to recharge it every night when it's less than half charged. You can keep the overall battery life/recharge life longer by only recharging when the battery is pretty low. Every once in a while, let it get down to 1 or 2% and recharge.

It's perfectly safe to leave it overnight as these new lithium batteries do NOT lose battery life like the older ones do, it also knows to stop charging once it reaches full charge.