Every vintage thread eventually hits the word "recap," so let me say the unpopular thing first: not every problem is capacitors, and not every capacitor problem needs the whole unit redone.
When capacitors actually matter: when they leak, when they bulge, when a fifty-year-old unit has symptoms that fit — hum from tired power-supply filters, drift no contact cleaning touches, one channel slowly going quiet. The quiet case is speaker crossovers: the original electrolytics drift, twenty percent, sometimes fifty, and the speaker slowly stops sounding like itself. Replacing them with film caps of the same value is one of the highest-value fixes in this hobby.
When they do not matter: when the real fault is a dirty switch, a stretched belt, a cold solder joint, or a foam surround gone to dust. Recapping a unit to fix a mechanical problem is paying to keep the problem.
The discipline I would offer: confirm the fault first, then fix that fault. And when you do replace parts, match values and ratings — especially fuses. "One size up is safer" has cooked more power supplies than I can count.
Your turn: have you done a recap that transformed a piece — or one that changed nothing at all? What did it teach you?