I've held Joy-Con controllers in the palm of my hand and repeatedly slammed my hands shut, with enough force to hurt me, while leaving the Joy-Cons as new (Samurai Training in 1-2 Switch is fun). They're really durable and in fact, after seeing and holding the Switch myself, I've never been more impressed with a piece of Nintendo hardware; it feels really robust and more like a piece of technology than the toy-feel of say, the 3DS or Gamecube.Slide on and off controllers looks to be asking for trouble to me.
I kinda wonder just how damage resistant they are. I give it maybe 30 minutes after launch, until somebody's already broken theirs.
I'm not sure the system as a whole would survive the "Accidental Kick Down The Stairs" test my clamshell New Nintendo 3DS has, but the Joy-Cons might (although I'd prefer not to test ).