The Bookmark list can get pretty much as full as you want it. Keep in mind that the longer the list, it can slow your Firefox install down.

What do you mean........Firefox Install?

I mean the Firefox you have on your computer can slow down if you put many (thousands) of bookmarks in it.

Firefox needs to check links in the bookmarks and history to update the visit status when present, so the longer that list is the longer it can take to perform this task.
If Firefox takes longer to respond then you can consider to move (export) some bookmarks to an HTML file and open that file in a tab instead.

What is an HTML file?

An HTML file is the same file that websites use to display their content.
In this case you get a file with <a href="http://">[link text]<\a>

See also:

• http://kb.mozillazine.org/Backing_up_and_restoring_bookmarks_-_Firefox

• Bookmarks > Show All Bookmarks > Import & Backup > Export HTML

Thanks for replying, however, it looks too complicated.