I plug mine in the first sign of frost. I apply every means of technology available to warm my vehicles (selfish motiviation is my own body warmth) including block heater, heated seats (leave 'em on in winter), window defrost set, and run the remote start for a few minutes. Add a hot cup of coffee and ready to battle Michigan winter (all in perspective)
Block heater alone nets me warm air within the 1st mile, as opposed to 3-4 miles.
Most Luxury cars include heated seats, heated mirrors, steering wheels, cup holders, heated rear seats, heated/cooled glove compartments.
F350 (approaching luxury import $
) heated seats, heated mirrors and a cord coming off my engine block. I'm making the most of what I've got