Do Nafion Dryers or Humidifiers Have an Expiration Date or a Shelf Life? Do they expire? – Nafion products do not have an expiration date, as the water transfer properties are a fundamental property of the material itself. The moisture transfer properties of Nafion do not change over time. We have seen dryers over 20 years old perform as new. However, we have noticed that there is a slight brown discoloration that occurs over time that does not affect the material, which was verified with our lab tests. To minimize this, the tubing should be kept in a black bag where it will not be exposed to light or UV.