24 hours with the door open.
Re: leaving the door open....
I think there is something in this idea. The in-rush of current as the compressor/pump starts is what's going to help break in the cord the fastest. So if you wait for the middle of summer and leave the door open, then turn the thermostat to the coldest position, the 'fridge is going to have to work hard to keep the temperature down. ;-)
So the system should be under a lot of load, cycling hard. That would hammer the power cord. Big motors that turn off and on a lot, like in washing machines, would be beneficial. I don't think you are interested in a steady state heavy draw of current (though that's helpful) - you want a lot of change over the break in time.
I agree with what everyone has said. It's the ebb and flow of current that seasons a powercord. If you don't want to leave your refrigerator or freezer doors open, leave the power cord in-line for 3-4 weeks. The owner of Elrod power cords told me this when I was breaking in one of his power cords. He reccomended a freezer, but a frige probably works just as well. Hope this helps. Stan
Addendum to my first post: The owner of Elrod Power cords said nothing about an open frige door. He said leave the power cord in-line for 3-4 weeks on a freezer, but he said, a refrigerator would probably work well too. This is the first I've heard about leaving the door open. I guess it won't hurt the cord, I don't know about the frige.