electrical connections - general discussion

This isn't a post asking for help, but something I just managed to fix caused me to wonder something - when electrical connections start to go bad is there a gradual drop off in efficiency of the function they take care of? Until this week I had assumed electrical connections were either working or not working, on or off. But what about still working but reduced performance? If performance drops off before failure there would be a case for routinely cleaning all the electrical connections. Same rationale as changing the oil.