If it passes certification you are set for years... I thought it was for 12, but it might be 5 as poislb said. I just trade tank's when empty. I let them worry about it. I paid $80 when I leased /bought my tank so a freebee that cost you $5-$10 to certify seems cheap to me.. On the other hand I like dropping a tank off and not waiting for it to be refilled which could be 10 minutes to a week..