How many of you use dual monitor setups

I have 3 monitors but I only use 2 atm, (1 is a shitty 16" square monitor but i mean its something). Atm i have a 24inch samsung tv and a 21.5 inch asus monitor. But I haven't got a very big desk and I keep my pc on the desk due to it getting filled with dust because I live in a old house.