At work, I have 2 Thunderbolt (2560x1440) displays and the laptop (15" Retina) on the side, mostly for email.
At home (I work from home often), I have two older 27" iMacs (both 2560x1440 - one acts as just a monitor) and an AOC 33" 2560x1440.
Nice part about the older 27" iMacs is they can be used as monitors when they outlive their normal use with Target Display mode and a mini-dp cable! 
Amazing how 10+ year-old Apple technology is still pretty decent! Not sure the newest Apple hardware will have that sort of longevity.