I don't think you can really clean an anode. Inspections are all you can do.
How long they last is based on the conditions of the water you put through the RV system........could be your own if you fill the onboard water tank, or certainly the campsites you visit. Some members say they empty the hot water tank after every camping adventure. Some like myself, drain and inspect the anode after every few camping adventures when they are only a few weeks between.
Your results may vary.
Ken and Terry
2018 Sunseeker 2430S with Trekker cap
and only rarely pushed by our 2017 GMC Terrain toad (4 wheels down)
Former Georgetown 330TS owner for 10 years with more mods than I can count.