I leave it on, much like my iPhone. Both stay plugged into a charger most of the time. There are various levels of "off". The lowest power draw is what you call off. You can use airplane mode to lower draw significantly when you are not near a charger or prevent connectivity to other devices etc.
Mine is always on. I'll plug in the charger once it's below 25% or so. Lasts for around 3 days... Piko
When I go to sleep, I turn it off. When I'm not using it during the day, I Leave it in sleep mode. Sometimes it doesn't like to stay turned off when I'm shutting it down while on the charger at night.
I leave it on. I started out turning it off with the idea of preserving battery life, but the amount it drains in sleep mode is negligible and it lasts a couple of days under normal use, so I no longer bother.
