Controversial topic so depends on who you ask as to what exactly it is and when exactly it is important.
I check it before a big case (especially the ones with anterior wear), when big cases are in temps, and prior to final delivery of cases. These are usually the same cases that get deprogrammed for a week to check how close they are to centric.
Here’s how I do it…..
Place a piece of 200 micron articulating film (Bausch) in patients anterior and have them chew on gum in the back. Any marks on facial of lowers and lingual of uppers are interferences as the gum is keeping the posteriors slightly apart.