Is there any evidence for the existence of helical spring wear in keyboard switches?
The primary documented (but not conclusively understood) wear is that of the plastic parts, but thin leaf contacts such as those in Futaba keyboards can also fail and need reshaping. With use, bounce time and contact resistance increases, and eventually this will go out of tolerance. With Cherry switches, chatter is the main mode of failure but that tends to be issues with new and comparatively young keyboards, not something I can recall being found in vintage examples. Generally, either the contacts stop working correctly, or the switch just feels bad, but to what extent if any do switches lose their spring strength?
Besides, surely weakening the spring by keeping it pressed is a wholly different issue to degradation from repeat compressions.
The awkward issue with failure is the simple question: do we only ever buy old keyboards that have not yet failed? That is, if a keyboard does see failure, is it discarded instead of sold on? This applies to not just the switches but keycap printing, leading if so to a false impression of failure rates and a false understanding of failure modes.
