I full time and the magnesium rod is about 70-80 percent eaten away at the 1 year mark. So I just replace every spring before leaving my winter hideaway.
As long as it lasts a year I will stay with magnesium. I want it to wear away and I'm worried that the aluminum version would not provide the same protection since it dissolves so much slower.
I also bought the cheap flexible hose end attachmnet which allows me to blast out all the gunk from the bottom of the tank. A side benefit to a yearly replacement schedule.
**** Do Not Forget - turn off the heating unit before draining the tank and replacing the anode. Running the electrical heater without water in the tank will burn it out.