depends on the markings, this was borrowed from
UkPSF
FIVE YEARS FOR FULL-FIBRE WRAPPED BOTTLES - EN12245 and Pi certified.
THREE YEARS FOR FULL WRAPPED BOTTLES - HSE-AL-FW2 manufactured before July 2003 then five years after retesting for SCI and Luxfer cylinders
THREE YEARS FOR FULL WRAPPED BOTTLES - HSE-AL-FW1
FIVE YEARS FOR HALF WARP BOTTLES
FIVE YEARS FOR ALUMINUM OR STEEL BOTTLES
hope this answers your question
dan