Bicycle Mechanics - When/why should I service cartridge bearing hubs?

In the old days with cup & cone bearings, I'm all over the concept of regular service. But with cartridge bearings, I'm not really sure what I'm doing taking the hub apart to just look at the little cartridge. Wheels are running smoothly and there's no play. Is there a point to opening them up?

I'm pretty sure I have cartridges on most/all my bikes. Shimano XT hubs on MTB and commuter, and I have Velomax Circuit Comp and Mavic Aksium on road bikes.

Seeing as I've screwed up a couple of non-bike things of late by trying to improve on adequacy, I'm in a risk averse mood lately. But for some reason I've got a burning desire to tear into these things.

In my experience with both mountain and road wheelsets (both Bontrager brand), the cartridge bearings seem to last forever.

I liked the old cup/cone hubs, mainly because I derived some sort of perverse thrill of cleaning, packing and adjusting the bearings.

However, in the past 6 years with the cartridge bearings, they've been maintenance free.

I guess that means more ride time, but I miss the intimacy of adjusting the hubs just right.

Ride on!

Eventually water or mud or whatever will cause the cartridge bearings to get rough but until then just leave them alone. The only inspection needed is to drop the wheels out and rotate the axle by hand for a feel of the bearing performance. If or when they ever become gritty and crunchy feeling then replace them.

XT does not have cartridge bearings. They are loose cup and cone bearings.

Yes, just replace them when they get rough. I know a road rider that just got 21,000 miles out his last set. A light bike and a lightweight guy too. Not really rough service, he does not ride in the rain either. I have a set with 6,500 on them and they feel like new. They are also on a bike I don't take in the rain.