Hi, thank you very much for the thoughtful review, and I'm glad you're enjoying Tab Stash!

You raise a great point about unloading tabs which might be doing something important (like playing music) in the background. Fortunately, Firefox allows extensions to detect when tabs are playing audio, so in future it should be possible to detect this and keep those tabs loaded—no configuration required. I went ahead and created an enhancement issue for this here: https://github.com/josh-berry/tab-stash/issues/90

Your regexp idea should also be possible though—if that's something you're still interested in, feel free to open another issue on GitHub!