I had two Blackvue cameras in my previous car (Focus RS) and had them connected solely to a permanent live 12v battery feed but with the BlackVue power magic module which monitors the battery voltage. I had swapped these cameras from car to car over many years and never suffered a flat battery. They were left on 24 hrs a day in parking mode, The draw was miniscule, and you can set the sensitivity to trigger recordings.
To be honest I wish I had transferred them to the Tesla as they are a much better system than Sentry mode - but I overestimated the value of Sentry prior to purchase. The BlackVue cameras were around £300 each so I've resisted buying new ones and installing to the Tesla as I'm retired and drive very few miles - the car is at home most of the time and in the garage.