You have to decide if the cost will be recouped by working quicker or when cold would freeze so you can carry on.
Some here use hot all year and say it makes a real difference, personally, never noticed much of a time difference between hot or cold whether that's regular cleans or manky one off work.
Hot is great during the winter months November to February for keeping the hoses supple and makes them easier to use.
I use immersion heaters in the tank cost £15 and heat overnight so prevent freezing as well
I couldn't get a written reply from my insurance company regarding lpg and as I employ can't take chances
Diesel systems are so highly priced I just don't see that you could get a return on your outlay
Darran