An older plumber told me you could extend the life of the older upright tank water heaters IF you drained them out once every summer.
Just hook a hose onto the bottom of the tank. Run the hose outside and turn on the valve.
He told me this as he was replacing the electric hot water tank exactly 6 months to the date after the prorated warranty expired.
My take on flushing water heaters was that they are largely self-cleaning now with the tube going to the bottom of the tank to constantly flush the bottom, avoiding that accumulation of minerals and pebbles from the old days.
Other than that my take was if you are the type of guy who likes that sort of thing then do it, but if you don’t care for those types of handyman chores skip it, and just get a new water heater when the old one goes bad.
Most people just want things installed and for them to work, but if you do drain your water heater remember not to run that hot water onto your grass or plants.
bkmk
A monel tank will never rot out.