"Heck, I've busted shock mounts just by hitting a pothole with no coil over spring before. "
My point exactly. It is the shock loads that are hard on things, not the steady loads. At least, steady loads within reason. One the other hand, on the typical half ton pickup that is only rated to carry around 1700lbs an extra few hundred pounds of lift would go a long way towards keeping the headlights pointed the right way with a full load in the back. I don't think that any sane person would ever suggest that you put the full weight of "a load a pickup truck will carry" on any supplementary springs. If you have busted shock mounts just by hitting a pothole you must either drive a lot rougher than anyone I know or the Michigan salt is sending your vehicles to an early grave.