Cat 3 approaches are only valid for 30 days. When the days remaining gets below 7 the company asks that we do a Cat 3 to restart the clock. It would suck if a plane timed out and it needed to get to a destination and was unable due to not Cat 3 certified. Also if a plane is written up in the maintenance log where it is no longer Cat 3 and maintenance fixes the problem, then the A/C will be due a Cat 3 check.

Thus the equipment checks.