Does anyone have this issue were firefox becomes slow if left open for a long time. In my case after a couple of weeks rendering becomes slow and when I use youtube for example if is laggy, just trying to change volume taka few second to show the volume bar. It also happens to my laptop at work. I have around 30 tabs open.
Have you tested with specific websites? Could it be a tab has some have JavaScript running constantly that’s causing the issue?
I haven’t tested it at my home laptops, but my work laptop all tabs become slow. I have to restart it every time.