I was in charge of medical supply for our brigade for fourteen years. Even triple sealed combat dressings stored on a shelf in a climate controlled facility would start to dry-rot after ten years (no elastic). My general rule of thumb for non-expiration-date marked medical supplies is thusly:
Stainless steel: inventory & clean annually
Wood: store away from light, inventory & clean annually. Toss when it begins to degrade
Plastic: inventory & clean annually, toss after ten years or when signs of "delamination" occur (peeling, etc).
Rubber/etc: store away from light, inventory & clean, toss after four years
Cloth: store away from light, inventory & clean, toss after eight years or when dry rot is found
Stick to marked expiration dates, unless gear has been "in the field" in which case it should be tossed every year, regardless of the expiration dates. This also holds true for unopened medication, triply so for medication that has been "re-packed".
Temperature extremes play heck with medical supplies. Don't store medications in the bathroom! The excessive humidity destroys them--in aspirin's case, a vinegary smell will be noticed when the container is opened. Most meds put off a musty smell when bad. PILLS SHOULD HAVE NO ODOR!
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Member of the toughest, meanest, deadliest, most unrelenting -- and ablest -- form of life in this section of space, a critter that can be killed but can't be tamed. --Robert A. Heinlein