Yep, provided they pass their test (and tanks which have only been used on land tend to last for ever) there is no set lifespan for them - expect at least 30+ years of life for steel tanks like this until expansion causes them to fail a test (some dive shops can be iffy about filling older (15 years +) aluminium tanks regardless of test, but that doesn't apply to this one as it's steel).
Have to say £120 is a bargain for a 12l 300bar - they're £200+ new.