Remember, that unless you are there to turn the water off, a leak can spill far more water than the tank holds. A bad one can literally gut several floors.
Cleaning will actually weaken the tank and it will break faster.
Get the best quality American-made one you can afford. Preferably a commercial one or at least from a manufacturer that also does commercial.
I meant to say that cleaning after such a long time would weaken the tank.
Otherwise, you should regularly flush the tank as recommended by the manufacturer.