I would like to add that I have been very pleased with my "Road Angel Connected" camera detector. I upgraded from the old style detector and yes it did cost a lot of money to do so, but the fact that the new one has no wires and updates itself makes it very convenient. You can also transfer it from one car to another which is another factor against hardwiring the unit.
In all honesty how many journeys of 4 hours plus do you make - when you do one of those you can always plug the unit in for a short while until you arrive, then let it recharge.
Just watch out for those cameras

however careful a driver you think you are.