[wisenull]

I am not sure if I understand your issue but if you close Firefox with CTRL+Q you get the same windows back when you launch it again.

[iszomer]

Unless Firefox crashes or you restarted after an update on Linux.

[wisenull]

I can't remember the last time Firefox crashed for me.

I also use it on Linux and after an update it reopens all the windows just fine (I get the message that I need to restart and just quit all windows).

[mozarella]

Use tab session manager. https://addons.mozilla.org/en-US/firefox/addon/tab-session-m...

[brokenmachine]

Firefox crashes every now and then, and I don't lose my session.