This time I decided to use the trick of wrapping some #14 or 12 copper wire around the calrod heater and extend it down the drain hole. But then I found there is a Whirlpool part 819043 to address this problem. It is an aluminum piece that clamps onto the calrod heater and extends down the drain hole. But it was too short for my Kenmore / Frigidaire.
So I made a similar device from some copper flashing (for roofing). The attached photo shows my copper handiwork next to the too-short aluminum Whirlpool part.
I will post again if it freezes up. Otherwise you know it is working as of today, 2-27-2012.
Also - does anyone have advice about using or ditching the existing "cap" that fits on the end of the drain line? It does allows water to pass. Not sure what its function is - maybe it prevents air from being drawn up into the freezer compartment? The attached photo shows the cap.