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?