On Saturday, May 18, 2019 at 8:22:32 AM UTC-7, Cursitor Doom wrote:

Here's what I found from a random selection of old components I snipped
out.
27k became 38.6k

another 27k ---- 29k

100k ---- 107k


Good to know, but the aging of composition resistors doesn't tell us much
about carbon film resistors (the common low-spec type nowadays) or
metal film (the common high-spec type) and manufacturer coatings
and such are likely to be changing from year to year as well.

Probably, because conductive (metallic or semimetallic) items are positive
valence, oxidation will raise resistance with time, for almost
anything. How much time, is still a mystery (for almost anything
we build today, at any rate).

There's too much chemistry involved to make a really good long-life
high accuracy projection for most real components. Humidity, ozone,
fungus, air pollution... so MANY variables.