I have the Tanis system on my S7 with the Rotax engine. I leave this system plugged in and on 24 hours a day. This was suggested by Tanis and although they say that an hour or so will heat the engine suffeciently leaving it on will not hurt the engine. The system will bring the temp up to 70 degrees above ambient temp. This also allows me to arrive at the airport any time and have the engine ready to fire up. Important with the Rotax as they suggest 122 degrees before takeoff.

That is another good reminder - having the engine warmed up to temp before takeoff. Fuel you save ground running a cold soaked engine to operating temp, versus one plugged in probably would more than pay for the heater and power.

I'm one of the "cheapskate" light bulb users, mine is a 125 watt heat bulb. I used to hang it under the engine on my C170 & C150TD, now with the C180 I stick it in the LH cowl door with a wool army blanket thrown over the top of the cowl.

I live in the Puget Sound area which generally doesn't get super cold, but below freezing temps at night are not uncommon. I don't want to have to go to the airport 4 hours before departure time to turn the engine heater on, I want it ready to go when I get there. I've thought many times about getting an oil pan heater pad, but from what I've read it's not a good idea to leave those on all the time. I know nowadays people are rigging up the power supply to a cellphone so you can in your pre-heat order, but I don't wanna do that either. Thought about an oil pan heater with a timer of some sort to cycle it on & off, but a low level steady heat is better IMHO.

I've been doing the heat lamp thing for over 15 years and (just like self-fueling out of plastic cans, another no-no according to most everyone) it's worked fine for me so far.