Hotpoint side-by-side frost free Refrigerator

Hotpoint side-by-side frost free Refrigerator Unit. I have replaced the Defrost Heating Element 3 times, each new one will run a few years, now a couple of months and then finally a month. I am suspecting the tstat or the defrost timer, but the tstat is new with last element. I do not want to keep throwing parts at it, but the wife is getting ready to throw it out and it works excellent other wise. Just checked all fans are working, but the 2nd element in two days is now burnt.