Bicycle Mechanics - Time to replace idler pulley?

I was replacing the chain on my Flora today, so of course I scrubbed everything up good. My rear derailleur (Shimano Alivio) pulleys looked pretty worn, lots of nylon fuzzies, and the idler pulley wobbled enough side-to-side that it touched either side of the cage. I replaced it. What are the usual criteria for replacing that and the jockey pulley?

On Shimano derailleurs designed for indexed shifting, the upper pulley has significant amounts of lateral slide by design. It's not very common for them to wear so much that their play becomes a problem. Usually the rest of the derailleur is starting to get sloppy if you have that much wear on it, in my experience.

The upper, jockey pulley had less lateral movement than the lower, idler pulley. I hadn't noticed any increased sloppiness in shifting, other than what I would expect at the "1" on the chain checker. Both pulleys look quite worn, the lower one more than the upper. I see pulleys in the catalogs all the time. Are they routinely changed, or should they last the life of the der?

Usually they last the life of the derailleur. I've had 5-year-old XTR derailleurs where the body pivots wore out before the pulleys did.

One exception was a derailleur I had where the lower pulley's pivot got mud in it (this was a ball-bearing pulley on another XTR) and didn't want to rotate. As a result, it experienced very rapid wear because the chain had to force it to turn and it didn't want to. The teeth on the pulley wore into little points under the abuse, which was caused by lots and lots of mud rides.

If your pulleys have trouble rotating, it's very simple to take them apart, clean the bushings and lubricate them with some Finish Line Century lube or most any other chain oil, or even grease.

Every few chain cleanings I pull the pulleys apart for a thorough cleaning and a little wipe of grease on the bushings. Just make sure you put the same parts back together and the guide pulley (has a G on it) on top, ie closest to the cogs.