[Boatanchors] Old resistor values

[Yong Surk Lee]

I found thousands of NOS resistors ranging from 1ohm to a few megohms at a
local hamfest. I believe these were made by Ohmite in the 50s or 60s. These
resistors are unused. Strangely measured values of most of these resistors
are about 10-20% higher than color coded values. Most of these are 0.25-2
watt and 5 or 10% tolerence resistors.
Here is my question. Does the resistor values increase as time passes even
if unused? Anybody experienced this?