So, without them, your axle will bend. So, even with them, your axle will bend. Trust me, I have seen it happen and right at the differential. Sleeves were a great idea and I even thought it was worth giving a try but, time has proven them to be pointless. Better to just play with what you have, spend a little money beefing up your shafts and then save the rest of your money until you can afford to upgrade to a ProRock 44. A bent axle housing won't leave you high and dry but a broken shaft or ring and pinion will.
Well, factory shafts do only have c-clips and they are prone to getting pried off. Once that happens, there's nothing left to hold the u-joint caps in place and that's the most common way a front shaft fails on the trail. Chromoly shafts with full circle clips will help prevent this from happening.