The terrapin should function without turning on or off the BT to save battery. The unit should connect, range, then sleep till the next press of the rangeing button which wakes the BT connection again.Excellent response from Vectronix. Since you spoke to CS, did you learn anything from them as to setup or usage?
It needs the latest update in the kestrel and the latest update for the Terrapin. There have been issues when either a kestrel or the terrapin have not had the latest updates which causes the two units not to connect. Not the issue I have☹ but a new one on the way.
There should not be heavy battery drain even using connected to the Kestrel.