It's a useful extension, but will always stop working. It must be fixed by turn off and on.
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May be from these,
Auto Tab Discard
https://addons.mozilla.org/en-US/firefox/addon/auto-tab-discard/
Sleep Mode
https://addons.mozilla.org/en-US/firefox/addon/sleep-mode/

Great and gentle extension. I expect to see it as a common function of ff preferences.

Great idea, great add on, but... not feet my needs :(

first questin, what is the grace period for ?

then, why only 3 stars : i have a lot of tab.... really a lot... i wish this could slowly load all of them

if i set like 10 tab left/right, firefox have really hard time loading them all at once. and if i cose firefox before finish to load, you loose everything

can you make an option to load all tab, but like, set how many tab at a time ?
(load 1st left/right tab, when finished to load, go to 2nd, wait finished then 3rd...
or, load 1st left/right, wait x seconds, then 2nd, wait, 3rd... until no more tab to load ? (waiting time can be change for slow/fast connexion)

if you can do that, then will definitvly deserve the 5 stars !

interesting idea