I was using the tab-state as a sort of short-term working memory and I don't think it was doing me any favours, particularly in terms of focus.
Now when I'm working on a project, I keep a list of relevant URLs in a text file (i.e. bookmarks but checked into source control).
I also use two browser windows, a regular one for "stateful" browsing, and a private-mode one for "stateless" browsing. Quick queries and exploratory research happens in the "stateless" session, with the understanding that I can close any of these tabs (or nuke the whole session) at any time without losing anything important. If I do come across something important, it gets noted down elsewhere.