Not that I want to appear overly negative but does it really matter. By the time you’ve got 16000 bookmarks it would be easier to Google the page you want anyway.
All I know is that I still haven’t been able to get to the end year for birthdays in the contacts. It can go past year 10,000 and that’s the farthest I’ve gotten. If that’s any indication as to how many bookmarks you can have then it’s probably a lot.