This is useful extension for managing several, several tabs that can often use up a lot of processing power on even a Macbook Pro. I think the only challenge I've had with it is that the sleeping tab sometimes cannot recover what page it was on, so I get a "close tab" error that hampers my workflow. I've observed this when Firefox updates, but also sometimes seemingly at random, and possibly when the browser is reopened in general. Sometimes I can navigate backwards in the browser to get mostly back to where I was, but sometimes not. I use tabs to section off different parts of my work that occur at different times of the day, so they are almost never closed. I need them to help me remember a task I have to perform, but also to have everything at-hand if I have to interrupt my flow to jump to that tab group when not focusing on it. It would be ideal if the sleep mode was able to handle for this case more smoothly. Otherwise, it does exactly what's described. Thank you for making this extension.