I think my first concert recorded with my JB3 was Govt Mule 10.19.02, so a little over two years ago. I record 60 to 70 shows per year and generally record the opening band. I also use my JB3 for transfers since I've never bothered to get a bit perfect digital soundcard to do transfers. So conservatively, I've put on about 500 recording hours, probably more like 600 or maybe 700 hours.
Never had any problems, other than a few times of operator error (forgetting to clear enough space on the hard drive for the show, not having the optical cable fully seated). All in all, it has been far more reliable than any of the 5 portable DAT decks I've owned.
Oh, BTW, I've only formatted the drive once in all this time, and I have never gotten any clicks or pops in my recordings, from a fragmented drive or anything else.