If you need a specific page available for reference purposes, bookmark it.
Tabs are volatile and the "restore last session" functionality in modern browsers is imperfect.
Honestly 1000 tabs wouldn't much of an issue if I had some SQL-like way to filter / group tabs to bookmark them rapidly in bunches.
Why not just bookmark them in folders once and for all?
If you need a specific page available for reference purposes, bookmark it.
Tabs are volatile and the "restore last session" functionality in modern browsers is imperfect.