Thanks to everyone who has replied to my post. It is now 4 years after my last post and my 66 gallon WH is 32 years old. When I replaced the magnesium anode at 30 years it was due but not quite down to the bare metal. I flush and drain it annually and still no rust. I am still amazed at the life of an ordinary WH which came originally with a 5 year warranty! So now I am beginning to form a theory for which I request any of your comments:
My brother has a household of 3, his first 52 gallon WH rusted out at 16 years, and his current WH is 40 gallons, now showing rust at 9 years. I am a one person household with a 66 gallon WH. Could it be that my brothers WHs fail because hot water is continually drained almost completely from the tank, then replaced with cold that hits warm glass repeatedly and causing it to crack and expose steel? Whereas I replace relatively less cold water which is preheated by the remaining hot water minimizing shock to the glass?
This seems probable to me however when I question any local residential or commercial plumbers they look at me like I am from Mars. If my theory is true then perhaps the use of glass in tank heaters could be replaced with some other material, allowing the use of small tanks with improved life spans. How about ceramic, which might also hold heat better than glass? Is it cost prohibitive? Thanks everyone, John.:)