You're looking at The Prepared (theprepared.org/newsletter), a weekly newsletter about manufacturing and other stuff! It's sent via Mailchimp, which automatically creates an archive URL for every email campaign you send.
The "view this in your browser" link was always personalized for tracking, not semantic, IIRC. It did include the actual content of "Hello, {first name} {last name}!" tags, which obviously wouldn't work here for every unique reader.
How long does this stick around? As long as you have a MailChimp account?
I guess I assumed that the URL was unique per-user and would be deleted after 30 days, because the primary use case of Mailchimp seems to be not-quite-spam "We're having a sale!" bulk campaigns.
I guess I just like being different.