Just revisited this. My dashcam was on 24/7 via pins in the overhead console lights, but my current shift pattern is making the car not used 4-5 days at a time and causes the battery to get low (The camera produces enough heat that the patch of windscreen above it has no dew on it!).
I decided to put it back to just coming on with the igniters as in years gone by.
I found this 4 pin plug for the lane departure camera has -ve on pin1 and switched 12V +ve on pin 3. What's more, R/C model plugs fit perfectly - the kind you get on R/C models for servos and receivers etc...
On the first picture is the internals of a USB charger encased in large clear heatshrink and hot-glued to the console and this is plugged into the pins of the camera 4 pin socket. The second photo shows the cable plugged in.
This is much better than how it was and will not whirr or buzz - sometimes the cables or charger would buzz when idling and had to bang my hand on the console.
Of course I know this is tempting fate and something will happen and I will wish it was still 24/7