There are differences depending on what apps you have installed and what you leave running if you put the IT into sleep mode. The default email app and Modest for example, will drain your IT pretty quickly if you have it set to notify you via the LED. Likewise, if you put the IT into sleep and it constantly attempts to connect to a wifi signal, but it can't, the battery will drain.

But, since the IT is built by a phone company, using similar technology, the best way to "put it away" is to put it in sleep mode (i.e., just like with a phone, it's possible to never turn it off). Sometimes, it's a good idea to switch it to Offline mode to avoid the wifi search dilemma.

But, you can turn it off too. There's no harm in that.

-T.