Suspension Bushing replacement intervals

[MandK]

So still going over Monty after returning home late last week and this morning when I lifted the tires off the ground enough to get a pry bar under them to check for suspension movement I knew I would be changing wet bolt bushings. I carry a four pack of bronze bushings by Dexter and a couple of spare wet bolts so I figured I might as well at least change the spring eye bushings on one axle while I wait for the rest of the bushings to arrive. My question is when you guys change these, do you generally see that the spring eye bushings need to be changed in as little as 10,000 miles? I have 15,000 on the trailer and the spring eye bushings were worn, cracked and broken, totally destroyed, but the Road Armor bushings were like new. Everything was tight when checked in the fall before we left so the spring eye bushings disintegrated in the last 4000 miles. Are the Road armor bushings superior to the Dexter brand and if so, where can I get them? Or is this the nature of the beast and I need to change my bushings every 18-24 months?
I grease them 3 times per year, which equates to about every 1800 miles. Thanks