At one point in the past, I had closer to 1600 in my main personal browser session, but when I moved to firefox I spent some time cleaning it up, and I'm sure a good number of them probably blew up during the move as well.
As you might imagine, I use a tab suspender extension to unload tabs and keep them unloaded until I choose to restore them, and switching browsers meant converting my suspended tab URLs from one format to another, which I built a script for, but there were a couple that didn't convert, and post migration I spent time cleaning that up and removing tabs that succumbed to link rot.
In addition, my work session is about 400 tabs at the moment.
Tab suspender is awesome