I see the same for 53 - horn. Am I right in understanding that in either case (horn or cigarette lighter) they can be switched to either on with ignition only or on constant, with no adverse effects? (other than the horn or cigarette lighter always being on of course).
If this is the case, think I will use the horn constant. Can think of no disadvantage to this given there have been times in the past with ignition off I have wanted to horn in other cars, parked up in car parks with others getting dangerously close, picking up passengers at the airport/station, etc.