Nate,
One thing about bronze......oil impregnated....like in pilot shaft bearings.....should be oiled, never greased! Grease will plug the tiny passages/holes in the bronze and then lube no more.....premature wear is end result. Made this mistake one time.....wore out the pilot bushing so badly that the trans wouldn't shift gears properly! (NOT a ZF......thankfully!)
Ford (60-70's) door hinge bearings, are another example....oil them, don't grease!
Makes me wonder if the bushings are actually bronze.....or if they should be lubed with a pressurized oil gun of sorts.
Anyone have they ZF service manual handy ......"periodic maintenance" section please! ??? 
Perhaps old grease had more oils? Less fillers???
Just my angle on these always over- ignored fittings.....
I'd give them a shot about every 2cnd-3rd oil change as a compromise.....well greased...then can't wear! Can't do that to a pilot bearing!
Steve