Do I need Bluetooth turned on all the time on my iPad?

Well now, that all depends. Do you have a device that you intend to pair with the iPad via Bluetooth?

Unless you are using bluetooth devices with the iPad, "all of the time" - There is no reason to leave bluetooth turned on "all of the time". It's that simple really.

I use BT devices with my iPad several times a day. I leave BT on because it's easier than turning it on and off. It uses negligibile amounts of battery when not actually connected.