Do you have a set of tabs that you leave open all the time in Firefox? I'm almost ashamed to admit I have eleven. That's right, eleven tabs that are always open in my Firefox, plus whatever else happens to be open. So the reality is that I always want to ensure those eleven tabs stay put, and don't get shut down by mistake. And I can also save some space because I use them so much that I know their favicons very well. So here's what I use:

PermaTabs - This is a Firefox extension that allows you to set a tab as a Permanent Tab, which means that it won't ever be closed. I prefer this to the Protect Tab functionality in TabMixPlus because PermaTabs simply shades the tab yellow, rather than putting an icon overlay on the favicon, which is what TabMixPlus does. If you're going to use my next extension, it makes use to install PermaTabs to make permanent tabs even if you're currently running TabMixPlus.

Faviconize - The Faviconize Firefox extension allows you to remove the text from a tab so that only the favicon is showing. As described above, this is perfect for sites you use regularly.

Together these two extensions add to the reliability and usability of Firefox, my browser of choice.