So, tonight with my feed-herder add-on:
* queried my browser history
* added an in-memory task queue
* enqueued 10000 tasks from my history to fetch pages and scan for RSS/Atom feeds
* set the concurrency to 32 for the hell of it
* hit the button and watched it go
Now my internet connection seems very angry with me. Twitch streams are dying. I'm glad I also added queue pause & clear buttons.