This problem started maybe 2-3 months ago. I used to have hundreds of tabs open for months and Firefox never lagged, never chugged even once. In the last few months this has been happening almost daily with only a small number of tabs open, as few as 10. The tabs I leave open are from only two websites (one of them is YouTube). Basically Firefox becomes unusably slow and needs to be restarted, so there is clearly a memory leak. I do not know if the memory leak is from Firefox, YouTube, or from the one other website I leave tabs open from, but I do know that this never happened before with vastly higher volume from the same websites.

The issue is not my computer hardware, which is in excellent condition and of excellent quality. This lag / freezing does not happen in any other application.