Kitchen Large Electric Appliances - Kenmore Refrigerator Water Leak - Drainage Tube Frozen

I have a Kenmore Refrigerator that continually leaks water inside the unit. This is a frost free unit, but I continually have to take everything out of the freezer, use a blow dryer to melt the ice built up inside the freezer unit, defrost the drainage tube, and then it works for about a month. Then, again, the drainage tube will freeze up, the defrost water cannot drain, and the water will again drain into the refrigerator unit.

Do I continue to constantly defrost month after month....or is there a way to fix this problem without replacing it altogether? My solution at the present time is keeping a huge pan inside the unit for the water to drain into, but I don't want to do this forever!