People can keep 5-10 things in their short term memory. Anything beyond that you can't feasibly multitask with so it should be a bookmark instead of a tab.
Maybe browsers should merge the two functions. (We already have pinned tabs too)
You can search through your open tabs by typing % followed by space in the search bar. I often do that since I tend to reference a lot of documentation/merge requests/admin interfaces/etc. and end up with quite a few tabs in a working session (usually clear them out the next day). Nowhere near 7000, though. Maybe 50.