There are times when the Firefox responds reluctantly. And it is not only when I have opened many tabs. But there are cases when I have opened as many as 20 tabs and Firefox is working fine and there are cases when I have opened just 5-6 tabs and Firefox behaves lazy.
So, I guess it do not depend on the number of tabs and there must be a specific tab which causes the problem. Isn't there a way to find that tab out and close only that instead of closing Firefox completely1? Is there an addon for that, or a script?