Just curious as how you all use your block heater. I am of the mind set that the more you use something the faster it will wear out so I try not to over use things if not needed. So that leads to:

 Is it better to leave it plugged in all night or possibly for a day or two at a time or would it be best to just plug in an hour or so before you fire it up?

 Any advantage to either practice?

 This morning the outside temp is 9° so I figured on plugging in an hour before start up today just to aid in warm up and easy cranking. It should start fine without it but I know it will be easier on the engine with a little heat in there.

Back when I daily drove my 05 I would use the block heater, not so much for better starting but for quicker heat. The 05 was VERY cold blooded and took 15-18 miles to get warm on a cold day. 
 

With a winter front installed I found that 90 minutes of block heater operation was optimal. In 90 minutes the block would get ~90% of the temp it would overnight at a fraction of the cost. It only took a couple weeks for the outdoor timer to pay for itself. 
 

I’ve only used the block heater on the 18 a couple times. It lives in a unheated shop most nights and even on really cold nights the shop doesn’t get too cold. The 18 also warms up much faster. 
 

On the 05 If I remembered to turn the heater to defrost it would do a great job keeping the windshield free of ice the next morning. It doesn’t take much heat for that, and there is enough connective movement of the coolant to get a little warm air to the windshield. 

For someone on a strict schedule timers work great but someone like me I might be at home for 3 to 4 days and never leave. Then at a random time like last week at about 3pm run out and to a rescue repair for a gal that lost here driveshaft. Still cold up here but using block heater for me would be very wasteful. I would have to leave it plugged in all the time. 

 

So 3 CYL high idle fills this gap much better and give me heat in under 5 to 6 minutes. No long waits for block heater to work and wasted electricity with 15 MPH wind blowing under the truck. I can get instant heat no issue. I'm not dependent on a electric plug for a block heater.

 

Like @Jthorfound out he's 7.3L Ford hates cold air and the glow plugs are not enough. I got his started without the block heater more our less by using a propane torch and warmed up the manifold tubing and it lit right off. No problem. His warms up pretty good just idling. 

 

Yeah we had a few days of near ZERO weather here now back to 31°F again.

3 cyl idle would probably warm up the truck, but when it's -30 you have to start the truck first.

 

39 minutes ago, Mopar1973Man said:

Yeah we had a few days of near ZERO weather here now back to 31°F again.

 

We just got done with 10 days where the HIGH temp never got above zero, and the lows down to -35* F. Extreme cold weather requires such things as high crank batteries and block heaters.

Not at all. Most of my job take me in to the back country away from access to power. I've never been REQUIRED to plug in to get started even with temps as low as -30°F and all I got to set the 3 cylinder high idle mode, now the grid heaters stay on the longest time giving the most heat to the manifold, now start the truck and leave idle. in about 1 to 2 minutes ECM will ramp up to 1200 and drop to 3 cylinder mode. If you want super fast warm up turn the exhaust brake it will drive the EGT's way up to about 800°F and the truck warm up like is driven on the highway. Usually completed in under 10 minutes. You can watch the ice melt off the windows in minutes. Rare I get the luck a vehicle happens to break down in a heated shop. (Yeah right!) Then they don't schedule there vehicle failure so I can plug in and set a timer. (Never happen). Since my life is very randon there is no way to make use of a block heater. But high idle is just as good.