Yup - degradation happens (sparkles) but it's when bandwidth becomes an issue with a specific cable / source.

It's nothing to do with the length of time a cable has been installed if all things are equal, however it's seldom that everything remains equal...

Connections corrode, cables twist in the wall / behind cabinets etc and HDMI ports get tweaked by overly heavy cabling + products being pushed against a cabinet due to overly tight install spaces.