The tags on my 1999, 2000, & 2001 Fire Bottles say they were "serviced" in Mar 2008 by a company in Morehead NC.
Last year, I pulled one "by mistake". Thick, semi-liquid crap dribbled out for more than an hour. It would have put out a match only if I had stuck the match into that crap.
Peace of mind, at least, says to not let Joe Blow just weigh the bottles and say they're good to go.
Mike