We've got 2 years on our test vehicle. Never lubed, only pressure washed, in Colorado. Other parts of the country are certainly worse for excessive road sale that seems to digest everything. Ours ends were all recently removed and checked, everything tight as they day they went in. Part of what helps it the joints are all with the bolt horizontal. This lets the ball get wiped clean, and not grim just sitting in a cup getting ground around like if the bolt was vertical.
Will they last forever, no. Will a rebuildable, jonny joint type unit last forever, no. Is rebuilding those joints easy after a year on the road, no. The snap ring or threads are corroded, and many times the joint is not rebuildable from corrosion alone. We've use rebuildable joints before, they just dont work as well as it seems like they would. And replacing a heim is easier, and cheaper than a rebuildable joint. These are some of the reasons we chose to use high quality heims over rebuild able joints.