I believe that the weak point of the bronze bushing kits is that the grease leaks out of the ends pretty fast. This leaves the bushing with little lubrication most of the time A kit that would seal the ends up would be the best solution. Of course a bronze bushing, even poorly lubricated is MUCH better than the stock plastic ones. But if someone could come up with a way to seal the ends, that would retrofit easily to all the springs out there, that would be a game changer.
I am presently using the Lippert Never Fail bushings which do not use grease. It is too soon for me to make a judgement on them, but if they hold up, then it would be a very good thing. Time will tell.