Prices for re-certification vary widely from state to state and even county to county. And when the re-certification expires, you'll have to do it all over again. I was considering re-certifying my two tanks when they were about to expire, but the price ($20+ per tank) in the area I live, made it an easy decision. I bought new tanks and recycled the old ones.
So do the math. It may be cheaper to just buy a new tank, and they're good for 12 years.