I currently have 20,097 tabs open in one browser profile. The oldest tab appears to be an HN post from 2.5 years ago, which must be the last time I swept tabs into bookmarks.

I used to sweep them more regularly, but Firefox + Sidebery don't even break a sweat with 20K tabs, apparently, so why bother?

The only downside is that it takes about 15 seconds for the browser to launch. I restart the browser whenever Firefox or macOS is updated, so every week or two.