It has been a while now, but when I closed my shop I went through ALL my resistors, including hundreds of old carbon comp types. I measured every one. Many were way out of tolerance, I had a bunch of old 20% ones as well as 5% and 10%. SO I kept 20% ones within tolerance, but tossed ones of same measure but 5% since they were out of tolerance if you dig.
Point being, you might sample a handful of old CC resistors to see if they have drifted over the years.