Yup, that D35 is a real POS! Why, it could blow up at any time! Mine is 20 yrs.old and still running the original shafts- and swingin' 33's on each end. I guess it's living on borrowed time... Oh yeah, it blew up the original TracLoc on the PO and he replaced it with a lunchbox locker. I guess the TracLoc couldn't handle 14.5X33" Boggers. When I bought the Wrangler, I put on 10.5X33" BFG MT's, regeared to 4.88, and installed a TruTrac in the front. It's been running 33's for at least 10 years with either a limited slip or a locker. It was babied by being used to build trails for our Jeep club (TRJC.com) and in two off-road parks. Heck, I gently used it on one of our more difficult trail complexes Sunday by running tailgunner behind a Built Jeep (King of the Hammers entrant). I made it thru a mud hole he didn't; of course, he made it thru some other places easily that required a lot of skinny pedal by me.
If you're running a lot of rocks and have to attack every obstacle with a full head of steam, then swap axles. If you like to finesse things and aren't in rocks a lot, then I'd say lock the D35 and carry some spare shafts if you're really worried. Yes, D35's do break; I've seen it happen, but I've also watched 44's and 60's break, too.