I generally give my engine an hour after 6pm, particularly as the nights get colder (unless I've been cruising all day).
I like to think it gives the batteries a top up, heats the water a little for morning use, and puts some warmth in the engine bay to assist (as winter draws on) with preventing any freezing. (Yes I know it's too early yet)
Besides, how are we to know when , between the hours of 8am and 8pm, is best going go suit you and anyone esle in the vicinity ?
I cannot see how this can be considered unreasonable or even worthy of query.
Rog