At work I have a docking station, that allows me to use two external screens with my laptop. And I find this extremely useful. I put a terminal window here, some source doe there, a similar source file over there, and I need to write a unit test while looking up things on Stack Overflow. So those three screens are easily filled.
Sometimes I work from home. I don't have a docking station at my place, and I can use only one external screen. This works as well, but often I miss the extra screen real estate. We do have a tablet though, mainly used by our children. Those are typically away or asleep when I code... So how difficult could it be to use the tablet as an external screen?