Has worked almost perfect so far Rated 4 out of 5 stars
I regularily end up with 50, 100 or a couple of hundred tabs.
At some point I got annoyed that even tabs who hadn't been used for hours would still eat CPU. Google search results was an example of this: Once or twice a minute it would ping my CPU for no good reason.
This extension unloads old tabs but doesn't close them. That way when I come back they just reload. You can also add exceptions for sites like youtube, in case you like to listen to videos in background tabs.
As others have mentioned it sometimes fails to capture state when Firefox is restarted.
Useless Rated 1 out of 5 stars
Interferes with the site save function when shutting down browser.
If you use this prepare to have most tabs not reappear after shut down.
Temporary fix Rated 3 out of 5 stars
This fix will not work with all tabs but it will work with most of them,
the fix is to uncheck bypass cache when restoring a tab option in addon settings.
works great... except after reopening the browser. Rated 3 out of 5 stars
Unloaded tabs at the time the browser is closed will appear as 'New Tab' once the session is resumed. I Don't often close the browser, but still a major problem. Other than that, Good Addon!
What others said - it's broken Rated 1 out of 5 stars
This add-on worked great up until FF 44.0.3. Since then there has been this annoying issue where unloaded tabs reload as blank tabs. 
Missing tabs Rated 2 out of 5 stars
Same problem reported by others here. Unloaded tabs becoming into "New Tab" and losing URL.
Tabs get lost Rated 1 out of 5 stars
I am encountering the same problem many reported already: Unloaded tabs get lost and cannot be recovered when Firefox crashes.
Thought this was great.... Rated 1 out of 5 stars
As other users have stated this add-on seems great to start with until you realize if firefox crashes there is no way to recover your tabs. There is a chrome plug-in that unloads tabs in a way that stores an app url in order to keep the page that the tab was last on so if a 'session' is recorded the page can be re-opened. Without this, this plug-in is useless.
Keep loosing tabs Rated 1 out of 5 stars
At first I thought it was a great addon, but then I discovered that I was loosing unloaded tabs after a Firefox restart. So in fact it now is useless.
Please update to work with latest FF Rated 3 out of 5 stars
This add-on worked great up until FF 44.0.3. Since then there has been this annoying issue where unloaded tabs reload as blank tabs. If like me you still need to use this add-on then I recommend installing FF 44.0.2 and disabling automatic FF updates. I would still really appreciate it if someone would fix the blank tab issue and update the add-on so it is compatible with the latest version of FF. Then I would consider giving this add-on a 5 star rating!
Broken Rated 1 out of 5 stars
It now turns unloaded tabs into blank tabs with not even history and no any way to restore.
If the original maker doesn't update it anymore, could someone take over please?
about:blank Rated 2 out of 5 stars
Like many here I keep loosing tab metadata without any reason
muy bueno cambio mi forma de navegar Rated 5 out of 5 stars
muy bueno cambio mi forma de navegar y hacer mas con mozilla.... ya no es tanto una relacion de amor odio con mozila....ahora es mas amor
Discontinued Rated 2 out of 5 stars
No fix anymore...This user has a previous review of this add-on.
Same issue as others Rated 4 out of 5 stars
The unloaded tabs become blank and lose the title and address after a restart. What are the alternatives and will there be a fix?
Double edged knife Rated 3 out of 5 stars
It is a great memory saver, but don't think your unloaded tabs will wait for you after FF closes or crashes.
This is the biggest and so far only flaw: If a tab is unloaded, and you close FF, the tab saves blank. Only solution is to go through your browser history and re-open the tabs manually - not very useful if your browsing sessions usually go over 10 tabs. Please fix this issue and you can have 5 stars from me.
Minimum Loaded Tabs Rated 3 out of 5 stars
Could you add the feature that we can set how many tabs have be opened to start unloading? Like if there are only 5 tabs open, the addon won't unload anything even after 10 mins cause it won't be necessary. But if there are more than 5 tabs open, it will start unloading and keep 5 most recent tabs open.
Lost suspended tabs when Firefox (45.0 and newer) is restarted Rated 3 out of 5 stars
I can't load tabs that were suspended before restarting Firefox (45.0 and newer). I was forced to revert to Firefox 44.0.2 :( I know that this is an old version of vulnerabilities, but I can not do.
The author, please reply to reviews with the same complaint when the has released a patched version.
Lost when restarted Rated 3 out of 5 stars
I can't load tabs that were suspended before restarting Firefox (45.0.2)
Good until firefox 44 Rated 4 out of 5 stars
Really, this was a very good plugin. when I installed it, it Works very nise, with sesión manager without problems. But, after the update of firefox44, the add-on only Works when the Firefox is open. If Firefox is closed, and the current sesión saved, wwhen you restart it, and load your previous sesión, the sesión that is saved with unload tabs, load the old unloaded tabs as about blank pages. In previous versions this problema doesn't appen. But currently it doesn't work. Please, update the add-on and fix it. Because this is better tan the other similar options. Thanks.