I can't say as I don't use air-tites, I do use the intercept and know when the inserts change to a brown color they have out lived their corrosion inhibiting properties and it's time to replace them. I use them on better copper coins to lessen the chance of moisture and corrosion on the surfaces now that I'm in a more humid environment (a far cry from Denver's dry arid air). I also keep desiccant packs with them and store them inside air tight Tupperware type containers, which are checked on regularly. I don't worry anywhere near as much on silver or gold coins.
"Buy the Book Before You Buy the Coin" - Aaron R. Feldman - "And read it" - Me 2013!
ANA Life Member #3288 in good standing since 1981, ANS, Early American Coppers Member (EAC), Colonial Coin Collectors Club member (C4), Conder Token Collector Club member (CTCC), Civil War Token Society (CWTS) member, Liberty Seated Collectors Club (LSCC) & Numismatic Bibliomania Society member (NBS), USMex, Member in good standing, 2¢ variety collector.
See my want page:
http://goccf.com/t/140440