How important is it to relegate expired medical gear to training and update with new?

For example, I have 3 x CAT 6 TQs, with exp dates of 2013 and 2014. One is in my range bag, one is kept in my emergency "bug in" kit and one is kept in my IFAK.

Same question for the other items that have exp dates but no medicines associated with them - Israeli Battle Dressings, Chest Seals, even some compressed gauze. Can these be kept for use (if not exposed to UV, left unsealed and protected from the environment other than from heat or cold) indefinitely? If not, is it because they "go bad", or just to ensure you get the latest and greatest version (for example - getting rid of my CAT 6 TQs for CAT 7s or upgrading to SOFTs)?

While I'm asking, what about Combat Gauze? Can it be used past its exp date, might it cause harm if it was, or might it just not work very well?