I think my limit is around 8-10 tabs, basically if I start having a hard time seeing the names of tabs I start pruning them.

Sometimes I like to go crazy wiki diving and middle clicking every link I think is interesting. I use tree style tabs plugin to help organize and it also makes it very easy to close the parent wiki tab to mass close when I’m done.

Downside is once in a rare moon my all of my plugins will crash and firefox will refuse to restore previous session