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Bluesky has gained a million new users in the last three days.
(www.theverge.com)
This is a most excellent place for technology news and articles.
If you consider it's the influx of new users, then yes, it does happen all the time. Do you have a different definition?
What's "eternal" in "Eternal September" is not the influx of new users, but rather the disruption of the social norms caused by a huge and sudden influx of new users.
That disruption started in 1993, and never ended. So it had a beginning but no end as of yet.