As one of the early adopters, I have been using this add-on from the time Quantum disabled "Sessions Manager". Over a year, this add-on has come close to the functionality of the "sessions manager" add-on by Michael Kraft. I must commend the dev, sienori on his relentless efforts through regular updates in helping the Firefox community. Kudos to the work! The only grouse I have though is that sometimes, I get the IndexDB erroe which surprisingly, automatically resolves itself in a few days. Can't blame for it. Have a good one dev! Cheers.