I had around 500 tabs open that failed to get restored beyond the first 10 when I shut Firefox down, which hadn't happened before. This extension brought them all back which saved me quite the headache. Of course, it couldn't bring back the groups from Tree Style Tab, but it was unrealistic to expect it to save another extension's data.

"Support tab groups" is false advertising -- or it's only true insofar as it will save the tabs /within/ tab groups just fine, as long as you didn't actually want to /keep/ those tab groups

over 5k tabs recovered from a saved file. could be improved but saved me big time

For years now Firefox session restore only puts the first window at the same position, the feature to let Tab Session Manager do this is golden as windows are now always restored in the same order. The easy access to auto session backups also golden. Together with Winger extension to stash windows, finally an upgraded browse experience which works nice and safe for 1000's of tabs over a 100 windows ; ))

While it's come a long way since its inception (I switched to this after a feature-rich and reliable session manager that I used was discontinued after Firefox's engine overhaul), it still seems to act up sometimes with too many tabs open.

Currently, this add-on just duplicates the saved windows I had open and doubles up on my memory usage. It doesn't seem like this is needed anymore with Firefox's native support.

WARNING!!!!! If you have more than 10 tabs open, this will overload the extension. As a self-defence mechanism, the extension deletes the saved session.
It cannot import a saved session containing more than 10 tabs.

In the case of tab groups, this add-on does not preserve original tabs grouping while importing a session: it imports all tabs uniformly, i.e. without any tab grouping. Dear developers, please, correct this fault. P.S. Yet pinned non-grouped tabs are imported correctly (as pinned).

Worked great for a long time, but in the last month or so, the "autosave sessions" feature hasn't worked at all. I've checked my sessions to try to find windows/tabs I wanted to go back to, and the last thing saved was over a month ago even though I know I had Firefox at least set to restore previous windows. But this extension didn't save ANYTHING over the last month+ even though I had it set to do so, so that feature doesn't do anything anymore apparently. I've lost dozens of sessions due to either a bug or recent updates, but either way this is bullshit.

I can't figure out if sessions are tied to virtual desktops when they are saved and is it really important to me

Garbage. Stopped working months ago. Literally never saves tabs. Don't waste your time. It also randomly deletes your sessions. Don't be tricked by the good reviews btw. They're old reviews from years ago when it actually worked.