Resistors

visually, you can see a transistor that has bone bad, you will know when you see one.

otherwise they last forever, most of mine from the 1960's are good, a handful replaced, cheap, easy solder job..

typical +/- 5% of their stated value in the old days, now +/- 2%,

can you hear the difference?

i typed transistor, but I meant resistor, they are the ones easy to spot and replace.