By a quality tank and it'll last longer than 6-10 years.

Not related to your post, but a humorous aside...

I recently replaced a water heater in one of our apartments. It was a six year rated GE that I installed in the summer of 2000. After I got home, my wife asked me:

Her: "Did you change the hot water heater?"
Me: "No"
Her: "I thought that's what you were doing. Why is the old one in your truck?"
Me: "That's the old cold water heater."

I then just stood there looking at her for a minute, and she then she got it.