Product review (4 stars): Time Will Tell
When I replaced the defrost unit the first time, it was the only thing I replaced and it only lasted a couple of months.  In retrospect, I probably should have replaced this along with the temperature sensor at the same time and the original defrost unit might still be working.  The jury is still out on this, however.  So far, so good.  Only drawback is that it didn't include clips and had to be spliced into the wiring of the thermostat that was removed.  Good value for the price, despite slow shipping.