If you have to replace your pins and bushings make sure your supplier or machine shop uses case hardened materials for both components.
If you use a soft material dust and dirt will embed into it, now this soft material will have fine particles like sandpaper in it, thus wearing out the harder material.
Example: Have you ever seen a worn hydraulic pump shaft and had wondered how could a rubber shaft seal wear a groove in a steel shaft.
Using case hardened material for both components reduces this problem for your pins.
Note: Most pins have some type of locking mechanism to keep them from turning to maintain this locking device (split pin, etc.) so that when the pin turns it only turns in the (greased) bushing.
At Hydrostatic Services we can custom make your case hardened pins and bushings from a large inventory of sizes.