At left is a new anode. In the middle is an anode at the point where it should generally be replaced. At right is what was left of the current anode when Lisa pulled it out of the water heater.
We have pretty hard water in Fernley. (It's safe to drink according to the water quality report; just full of minerals.) When Lisa pulled out the anode and drained the water heater, you can see on the ground below some of the mineral accumulation that washed out.
After filling and flushing the water heater several times and scrubbing at it with a wire brush and a probe, Lisa got most of the accumulated crud out of the water heater, put in the new anode, and all is well. She says we have to make a point of replacing that anode far more often than she has been doing.