All of the standard plastic bushings in our last TT were completely shot in just the 2,000+ mile delivery trip from Indiana to our dealer on the west coast. Not impressed with these bushings. I would hazard a guess that there are a lot of trailer owners running around with bad bushings and won't know until something doesn't seem right or fails. For the cost of the Never Fail bushings, not sure why they don't just install them in the first place. (Wait, I do know...)
Before installing any type/brand of new bushings, if it were me, I'd want to check the spring hangers for correct mounting/location and any other potential suspension/frame issues that could possibly lead to damaging new bushings.