Got my FW new, mid August 2012. My anode looked good end of October, when I flushed the heater, and stored the FW. I made it through 13 with it, but put new in this year in May. This one will finish the season, but I think I'll need new again in may.
Mine are magnesium. Manufacturer recommends using aluminum, only if the mag does not last 6 months to a year.
I flush mine several times a season, using the long thin wand I purchased. I get lots of crud out, and the water sure is gray murky looking. I usually have city water in it.
Jerry