I just re-did all the R's and C's in the preamp section of an aged Dynaco SCA-80. It was interesting to measure the resistors to see how they had changed.
The design has mostly half-watt 5% carbon comp resistors, with a few 10% resistors. I measured them all, and in comparison to their original values, they all had gone high. It ranged from 4% to 14% high. On average, the resistors were 8.24% higher than their nominal values. I measured 34 resistors.