This is very good. I have loads of tabs open simultaneously and was having problems with high memory usage. This plugin instantly took care of the problem. The configuration can seem a bit daunting at first but it's worth taking the time to go through and understand every setting to get the the most out of this add-in.

I notice certain "special tabs" are not being discarded, for example, Sidebery folder tabs, Firefox Preferences pages, and add-on options pages. Regarding Sidebery folder tabs, perhaps they are being seen as active all the time because Sidebery is active and those tabs are part of it? This doesn't bother me, but I thought I'd mention it in case it's not intentional.

My only tiny criticism would be the lack of documentation, since some settings are somewhat cryptic especially if you are not a techie. Eventually I managed to figure out almost every setting through trial and error.

I'd like to sugges a floating Save Options button that's always visible, thereby eliminating the need to scroll down to the bottom each time settings need saving. This would make experimentation less time-consuming.

In short: A fantastic add-on. Big thank you to the author/authors!