Defrosting the Refrig

When is the right time to defrost the refrig? My freezer is frosted over on the back. Should I defrost now or let it build up a little more?
Is the refrig having to work harder?

If the fins at the back of the refrigirator are iced up and the back of the freezer is frosted over, it's time to defrost. If you have a cooler, put your frozen stuff on the bottom and cold stuff on top. Defrosting should take about 90 minutes. We have to do this about twice a season due to humidity in NC. It's almost unavoidable when the reefer is used long term.