My standard browsing habit consists of launching browser with 1 pinned tab and 1 home page (so 2 tabs only), then opening 5-10 tabs from my bookmarks, checking pages then closing them and leaving only 1 pinned page open.
After updating from 77 (I think it was 77.0.2?) to 78.0.1 I started noticing terrible firefox performance after a few minutes of browsing.