When I had to reimage from Win10 to Win11, I used the Firefox Sync feature to ensure that the machine name I was going to reimage had the 'Tabs from other devices' in the sidebar of my other devices - accessible and reassuringly present. It seemed to be working like a charm - once reimaged, on the new computer image I could go into the old PC name's list of tabs and bring them over as needed. Roughly 30 days after that old computer name had been online, that computer name and all of its tabs were GONE from the list of devices. No warning. No prompt. No dialog stating I have a certain number a days of access to that machine's tabs. NOTHING.
Why have a feature that is going to disappoint your user base?! Use bookmarks, you might say? What if I hadn't bookmarked the tab yet? Why not keep that offline system persistent or AT LEAST warn the user of the impending deletion/removal?