Peyton300TD,
I believe most block heaters have some sort of cut-off when they reach a given temp. You may try using a timer & set it for only a couple of hours before starting to save electricity. In Texas I had a no-cost-to-me source of power so I plugged it in the night before. Never wore out the heater. On the 220D it was a great to get in the car on a cold morning and see the temp needle already off the peg before you even started it!