I think timestamps are even more important in that case.

Which timestamp is relevant on the body of a Wikipedia article that has been maintained for 15 years?

All of them, which his why Wikipedia maintains an edit history.

At the very least you should provide the inital publish date and last update.

Doesn't provide an edit history in the article, though.

You can include an edit timestamp.

This still sort of codifies the edit is a discrete event, and not an ongoing process.

That's a good thing, because that final edit is a discrete event. At some point this ongoing process will end and the edits will stop. The people engaged in the process will likely forget or not be available to add a final timestamp, but an aging edit timestamp will automatically indicate this moment in time.

It is always and ongoing process until it isn't. Knowing if/when the transition happened is useful.

A bit like a file with a created and updated timestamp then?