RCVs seem like the last stop when you are upgrading a D30. When you get that much shaft in a D30, you want it to be trussed & with a full case locker, too, or you are putting the center section at risk.
If you are going to build a D30 that far, you are basically trying to duplicate the strength of a D44 with shafts / joints in it or a D60. There are reasons to choose any of the 3 axles.
I wouldn't run RCVs without having a truss & full case, though, simply because I don't want the "guts" to be the weakest link in the axle.
If you run them with a fully beef'd housing & carrier, though, I think you'd be able to beat it up pretty bad on 35s without any real issues. Going bigger.. well... I dunno about that...
Bottom line is that the RCV is *hella* strong, which has its pros and cons about it. All depends on where you want to go with the axle, gears, tires, terrain.