It takes a very long time for my car to properly defrost. I just bought it this past Fall and this is the first winter I have it.

Any tips/suggestions for troubleshooting this problem?

check fuse for proper size , check the connection on the window the connecter might be dirty or loose. see if the wire is not loose or has been cut , i may be grounding out.

Make sure you don't have leaking tail lights. Check for water in the trunk to be sure. I know it sounds a little strange, but if their is a high concentration on moisture inside the car, defrosting will take FOREVER. Something to consider.

Also make sure you have the circulation knob set to outside air, rather than recirculation. But you probably already knew that. :)