Saeculum as a unit of time

The measurement of time has been capturing my attention of late, typically while walking the dog in the quiet of night. It might be dark and gently raining, or clear and crisp with Orion overhead. The word on which my mind has circled is saeculum. The word is uncommon in this form but also the predecessor to "secular" as the worldly age. The idea has been watered down to mean the "length of time roughly equal to the potential lifetime of a person, or equivalently, the complete renewal of a human population" so sayeth Wikipedia.

More interesting is an "original" meaning -- "the time from the moment that something happened (for example the founding of a city) until the point in time that all people who had lived at that moment had died." This is a relative duration that resides across the collective consciousness of all perceivers of that event.

What manner of event warrants a saeculum?

In how many saecula can an individual participate?

Who adjudicates the coming and passing of saecula?

How do the changing and failing memories of members to the saeculum change its composition?

There is the idea of this duration strictly as a span of time -- a measurement of duration. There too is the idea of "in living memory" -- the event and its characteristics, unless captured and committed to media appropriate to the technology of the time, expiring when all its direct observers have died. Most of human operated in this fashion. Media was oral and very malleable, then written with various technologies, now hard drives mostly. Is the COVID-19 pandemic, as a planetary event, a candidate for the largest saeculum in human history, and just underway?

It is also possible that I am attuning more to my own mortality.