I have tippet spools that are years old and in good shape. If I have any question about it I use my Berkley fish scale and test it. I will cut 2 ft off tie in loop knots both ends. Then test with a study hand pull. Once it breaks have a reading to decide does it stay or go on the bench for fly tying. I keep my tippet in the house where it is cool and in the dark away from sunlight.