How often do you replace pulley wheels?
 

My pulley wheels attract lots of crud and some fibers wrap around the pivots. But they seem to work fine. I don't think I've ever pulled them apart, but it seems like that might be the only effective way to clean them and get rid of the gunk.
Do YOU do this on your bikes?
But if I do that, should I have spare pulleys and/or pivots on hand? If so, from where?
Thanks

Most derailleur pulleys use simple sleeve bearings, which are dead-easy to clean. Some fancier models may have sealed cartridge bearings, which shouldn't need service. And some old-school derailleurs actually use loose balls in a cup-and-cone system.

There's no compelling need to replace them unless the pulley falls apart. I have some that are 30-40 years old and still going strong.

They're easy enough to remove, clean, lube, and re-install. Requires a hex wrench and 15 minutes of your day.

On a Shimano 600EX, I replaced the jockey wheels after 25,000 mi over 30 years - I kept them clean that long.
On an Ultegra 6500 bought used on ebay in VG+ condition, replaced them right away before using the RD.

On my Microshift R10, I replaced them after a couple of thousand miles because I ran across a crazy Amazon deal - Microshift sealed ball-bearing/ alloy for $12/pair - I grabbed them. Next time I looked, they were $24/pair and very soon sold out

http://img.photobucket.com/albums/v7...aP5030001a.jpg