Since I'm talking about 20- and 30-yr-old bikes, I'm posting this here rather than in the Mechanics's section.
If the shoes look like they're in good shape and aren't too scuffed up or dirty, do you still replace them? Some people--and Sheldon Brown's site--say that "pads get old and brittle and should be replaced." A guy at my LBS who's into vintage bikes said he himself rides his vintage '82 road frame and has never replaced the shoes, it's not necessary. Other than pieces of material lodged into the shoes themselves, do you look for any particular signs they should be replaced? I hate wasting stuff just because.