The ruling on all steel tanks is as long as DOT (The Department of Transportation) has not pulled the exception on the bottle, they will last forever. Unless the do not pass a hydrostatic test that has to be done every 5 years on most steel tanks, 3 years on aluminum and composite, 12 years on storage tanks. Composite and hoop wrap bottles have a bottle life of 15 years. I do have the joy of maintaining all the air bottles on my Fire department and sending them out for Hydro testing. If you go to a scuba shop or just look in the yellow pages for a hydro testing facility the cost should range from about $10- $35 for hydro testing of your own bottles.