Dr.SportsMedIN said:

It helps to ask what evidence would change your mind before you look at any.

There is a second half to this that has not been said yet. The single most useful discipline is bringing the whole panel to a clinician rather than one flagged value. One out-of-range result in isolation generates anxiety and unnecessary tests; the same result next to the trend and the rest of the panel usually generates a shrug.

Adding the numbers, since they settle part of this. For anyone reading later: the numbers in this thread are worth checking against a primary source before you act on them, including mine. Half the figures circulating in this community trace back to a secondary summary that dropped a qualifier.

A narrower follow-up, since the general answer is now clear:

How often to repeat it, because quarterly seems to be the convention and I cannot find the reasoning?

dave_SLC said:

For anyone reading later: the numbers in this thread are worth checking against a primary source before you act on them, including mine.

I do not accept the framing. The question has been narrowed to the version that has a tidy answer, and the part that was dropped is the part the OP actually asked about.

Correct me if the detail matters more than I have assumed.

Closing the loop on my own question.

Resolved, and the thing that resolved it was the least interesting suggestion in the thread. Writing that down for the next person who wants the interesting answer.