What in the world do you put on those other seven screens?
I can't think of a situation where I'd need to focus on all the things you list simultaneously – even just having e-mail on the screen while I'm trying to code is distracting – so I'd rather have them hidden. Sure, I'll have a couple code windows and documentation or logs open, but that fits with room to spare on a single monitor.
> offline documentation (i.e., not in a web browser)
This deeply confuses me. Why does it matter if the documentation is in a browser or not?
man and info come distraction-free out of the box.
(And before you ask: Yes, I use one laptop screen for all my work.)
The only people I know using 4+ screens are monitoring Satellites or industrial processing equipment.