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.