This is probably my favourite add-on. I organise my browsing using this rather than bookmarks (mostly).
The reason I haven't awarded 5-stars though is that I remember its predecessor, and the feature I really miss that that possessed was AUTOMATIC save to the SAME named session. (This would also reduce the vast propagation of sessions, at least for me)
I wonder if some unique identifier could be assigned to a session, and, if the user has chosen to "yes" a hypothetical "automatic overwrite/replace" setting, then, instead of saving to a new session it simply overwrites the old, therefore retaining the old name .... ?
I'd love to see such a feature added.