I haven't babied my JB3 like Chuck has. that's not to say I purposefully abuse it, but I used it as an mp3 player for a while before I got into recording (before they had firmware with level meters). I used it in the car, at work, etc, and carried it around from place to place. Hell, I even spilled a glass of wine on it once(while recording a show. Ooops). Pulled the batteries and let it dry off, pulled it apart and cleaned everything with isopropyl alcohol, and it works just like new.
Now that I'm recording with it, I don't use it for much else. Take much better care of it. But it's gotten some abuse, and it's held up quite well. I've had it for about a year and a half now. Not sure how long I expect it to last, but just wanted to share my experience with giving it a beating and having it hold up quite well.
Also, I run a UA-5 in front of it.