I have one window per "task" (like if I'm looking up how to do something using some API, I'll have a single window for that, with new tabs for API docs, some stackoverflow responses, etc), and when I'm done with the task I'll close the window.

Windows for "idle browsing" get closed the next day when I open up my computer and look at the tabs and think "well this sounds boring, let's see what new has happened overnight".

On my phone OTOH, the tabs just stack up until twice a year I just mass-close them all.