@ansuz Think "several thousand tabs". I have many different projects that I switch between a lot (ADHD, so no reliable focus control), and if each project needs 50-100 tabs for various research purposes, it quickly racks up the total.

(FWIW, I think Firefox is mostly fine at handling a lot of tabs, it does so better than Chrome. It does have pretty bad failure recovery, but that's probably not specific to having lots of tabs, and I've also seen apparent resource leaks with low numbers of tabs.)