I've got around 300 open on my phone (Firefox for Android) and 1400 on my work PC (Firefox on Windows)... I need to close the one day. Some might have important stuff open in them though!
I have a Pinboard account I use for bookmarks (joined when it was just a once-off fee to join) but I want to move to something self-hosted at some point. I like having a web UI with full-text search for bookmarks, and being able to use the same bookmarks list across browsers and devices.
One tab literally takes multiple minutes to stash my tabs because I have so many... I do like knowing that my tabs could theoretically be searched and I could find them, so occasionally I use it to close windows instead of going through them first
One of these days I want to make a tab bookmarker that will handle sites with comics/novels...I don't care about the history with those, I just open tabs for stuff I'd like to read, and keep tabs to save my place when I switch works (eventually I recognize I'm not going to finish them anytime soon and close them)
I also open windows when I research a new topic, so I can probably do something with that too