Yes, if you “turn off” the tablet with the “on” button, depending on how it is configured, you may only putting the tablet to sleep. If asleep, the tablet will continue to be “on” and will continue to use battery. If it is not shut down properly, the tablet could have a depleted battery when you go to use it again.
Alternatively, it is not advisable to continuously hold the power button to shut the tablet off. This will force the unit off. If done frequently, this can cause issues.