weeellll... EZ Test say it can last up to a year, ChemSol say you should get a new one every 6 months just to be sure, Dancesafe don't really have a policy AFAIK. I think the best thing to do is just monitor it's colour and reactivity. If it goes brown, or stops reacting to a test sample (like aspirin) then it's time for a new one. Your test sample probably shouldn't be an MDxx pill, as when the testers go "bad" they stop being selective top what makes em turn black. The aspirin reaction (bright red) is the one to check with.
