Hi, I'm really sorry to hear it's not working on your configuration. I have a question though, do you use any kind of tab unloading extension, or some session managers? I develop this extension having 2500 tabs open on average, for the heaviest use case scenario and it should work. The thing is, it's not compatible with unloading tabs extensions, because extensions can't communicate to each other in new Firefox.

UPDATE: I'm glad it works now. You are absolutely right, I should warn people about this limitation. I will try to add that to description, but there is a limit of description length, so I had to keep it short.
I have in plans implementing a built in session manager, but it won't happen anytime soon. But I need it too, so it will be there someday. :)