Contrary to a lot of stuff you read here, and I might add some brought on by CS customer service. A reasonable length of a heavy (cord 14 gauge or heavier) should not cause any problem with a Smokette. Like 50 feet should not be a problem. The specs on a Smokette says it is 500 watts, 10 amps. The heater in the smokette is either on or off, and that is governed by the thermostat and its placement within the Smokette, another line completely and has absolutely nothing to do with any extension cord. When the heater is on it draws, very approximately, about as much power as your computer and monitor. Much less than your 72" wide screen TV.
However, your house wiring is a different story. If you are running the Smokette off an outlet in the back 40, that is strung with 14 wire you should not run an extension cord at all and move the smoker closer to the house panel. Modern electrical codes only require number 12 wire in bath rooms, kitchens, laundry, and similar areas. To save a few bucks in the construction, every thing else is wired with number 14. Solid wire will not carry marginally as much current (amperage) as twisted wire (extension cords). So if your electrical service comes in on one end of the house and the outlet you want to run it off is an add on to a plug in your living room a hundred feet away, no extension cord should be used at all.
For years I have done hardwood floors that use a lot of power especially on 120 volt currents. There are way too many houses that we have found that just won't run that equipment properly off the house wiring and we end up running off extension cords run from the kitchen, bath etc. With that equipment I will not run anything on less than a number 12 cord greater than 50 feet.
So to put this in some sort of perspective, just because you can plug in your smokette into the outlet, doesn't mean you should.
I hope that helps.