I'm working on tab garbage collection too!

https://github.com/echelon/browser-focus

I need to add screenshots.

Basically puts an overlay on all timed out tabs, shows all timed out tabs so you can kill them all together, etc.

I want a better algorithm / heuristic that can semantically track what I'm doing.

I might eventually be brave enough to break out of tabs and let my windowing system handle everything.