There's also an [Experimental]
add-on called Dormancy (https://addons.mozilla.org/en-us/firefo ... y/reviews/
) that claims to 'retire' long unused background tabs (sort of a reverse tabs on demand). It sort of works, but alas, it has at least one killer quirk in that it renames tabs with nondescript gobbledegook like "data:text/html...xyz</title>".
As far as I can tell, Dormancy and Suspend-Backgrounds perform different tasks. If the developers of the two could co-operate to produce a single 'killer' add-on, it could produce a significant performance boost. It would be nice to see this sort of functionality incorporated into Mozilla Firefox proper. For all the tinkering they've done with Firefox v4.0, it's still a lumbering beast when it has a tab clogged session running for more than an hour or two (especially when using TMP's otherwise superior session manager).
Thanks @onemen for the above tip by the way. It has definitely sped up my browser no end. I suspect that their may be some blow back for certain fringe cases where I actually want background tabs to continue executing 'actions'. That said, I haven't found one yet.