We don't full-time, so my water heater mostly sits shut off w/o power. Still, every Fall, when I remove the anode rod to winterize, it's a throw-away - almost completely dissolved.
I always replace with the OEM magnesium because that was the default in the manual. It also says for people who experience rapid dissolving or special water conditions, the aluminum dissolves slower - but of course that gives less protection. I know it's a sacrificial anode and it's job is to dissolve, but I might try aluminum this year.
Mike & Pam '12 36RL, Kodiak Discs, 17.5" G114s H-Rated, SRE4000 w/HD Shackles, Joy Rider Shocks, Flex Air, 5.5 Onan, W&D, DW, 4 Scare Lights, (2) 6V Trojan T-145s; Progressive EMS-HW50C, Winegard DTV Sat, Sony/Denon 4K Home Theater, WiFiRanger EliteAC Pack, weBoost 4G-X Cell Booster.
2020 RAM 3500 Limited CC, LB, 4x4, DRW, Cummins HO, AISIN, 4.10, Curt A30 w/OEM Prep, Transfer Flow 70gal Aux Tank/Toolbox.