Looking at an older (2002) 4wd magazine there is an ad for joints by CTM (CTMracing.com) that advertise as super heavy duty rebuildable front u-joints. The best thing I can say is regular maintenance to keep them from drying up, which is the only cause I've ever seen for them failing (yes they break, but I've only read about that). If you traverse a lot of deep water that will kill them faster than normal highway driving. Typically the front ones are non-greaseable because the holes that go through the body theoretically weaken the joint. Not as much of a problem on the driveshafts because the angles aren't as extreme, but on the front axles when turning sharply and hammering on the gas it's brutal. Call any of the higher end companies like Spicer to see what they have. I recently bought rear driveshaft u-joints through Randy's Ring and Pinion (deals with Spicer) and got great service but socked with a $14 shipping bill for one u-joint! :doh:
