I replace them if they reek of mouse pee. There's not much you can do about that. Other than that, you can do a lot of repair to cabinets and hide the repairs under a good even coat of paint.
Sometimes the hardware cleans up nice, sometimes it needs a can of spray paint, occasionally, it needs to be replaced.
Paint job has to be top quality and inside and out.
If the configuration of the kitchen is changed, that usually means new cabinets; it's too hard to match old ones.
With some cabinets, you can replace the panels on the doors with glass (tempered safety glass) and a few top cabinets with glass doors really dress up a kitchen.