1,740 tabs open right now on my wife's Firefox and it seems to be operating just fine. Sounds like something's wrong with your Firefox. I recommend a refresh which can be found under about:support
10, 20, even 30 i can understand. More is the equivalent of forgetting to empty the kitchen trash can and still filling it until the smell is horrible.
someone got to tell her there is a cross on the right to close the tab.
