1480 Shaft ears went first best I can tell, I kept the factory lockouts thinking they'd be an easily replaceable componet and they'd fail first. Apparently the factory lockouts are pretty strong though because it ripped the ears of the stock 1480 shaft and did nothing to the lockout. The actual shafts themselves seem like quality shafts, but the ujoint ears stretched on mine very quickly. I upgraded with $350 worth of OEM 1550 shafts and a couple rides later blew up a factory lockout. Replaced that lockout and still going, of course its not as tough as RCVs but its also out being wheeled instead of sitting on jackstands waiting on high $ parts. So far the 1550 shafts have proven to be quite tough, only thing I did was tack the u joint caps just for extra peace of mind since I know I'm not going to keep an eye on them like I should.
Also one VERY IMPORTANT thing I learned about using the lockouts as a fuse is when they fail the wedge themselves in the unit bearing and will not come out. It seems like it wouldnt be a problem because you could just pull the axleshaft out of the unit bearing and knock the pieces out, but since the snap ring that retains the shaft to the unit bearing is underneath the lockout you cannot access it to remove the shaft. There are two solutions to this issue that I have come up with. One option is to not run the snap ring on the stub axle, that way when the lockout wedges in a unit bearing you can pull the unit bearing and knock out the pieces of lockout. That option only helps if you had disassembled it prior to breaking the lockout and removed the snap ring. I did find a second way to get around this problem. If you have a medium sized pair of 90* internal snap ring pliers (I had to buy a set). You can remove the unit bearing with the shaft still attached, then turn it over and use the snap ring pliers to remove the large snap ring that holds the axleshaft bearing into the unit bearing. Once that snap ring is gone you can knock the and bearing shaft out through the rear as an assembly. Of course option 2 also means you have to either not have the big vacuum seal on the shaft, or you'd have to destroy it to get at the snap ring. Hopefully that makes sense.