I can't tell you how many vehicles I've owned with a non-working rear defroster. I've had so many that I stopped trying, until one morning I accidentally hit the rear defrost switch and saw lines of clear window appear before my eyes. I also lived in Georgia, so rear defrosters were an unnecessary novelty for the most part. Now that I live in the Northeast I recognize the value of that grid on my back window. When it's not working, I'm upset. If your rear defroster has stopped working, you can easily find out where the problem is, and then you can fix it yourself. Check out this Rear Defroster Troubleshooting Guide
that has complete instructions on how to figure out what's wrong with it. You don't have to live like this, and winter's coming!