Chombi

Despite some naysayers, I think sealed cartridge bearings on components are still generally a good thing as their very slow rates of wear fits the needs of most cyclists out there who do not want to have to regularly service/regrease loose bearings on their bikes. Yes, there is a question on how most will handle having to eventually replace the cartridges if they do not have the right tools to do it, but in most cases, I think people might look at their sealed bearing components as long interval replacement items as their wear rates are generally so long that it does not really get in the way of their cycling till that point and most just opt for replacment of the whole component.
Trick to seaeld bearing components is to try and avoid getting used one in the first place when building up a bike. Getting an NOS item will give you the benefit of the longest use you can get out of them before wear ever becomes an issue. And in the end, if you do have to replace the bearing cartridges many years later, it's not impossible and many resourceful cyclcist have succesfully extracted them and replaced them using home made tools and careful planning. I know many motorcyclists do it with their pressed in wheel bearings all the time. I don't see why it might be that much harder to do with bicycle "stuff".
My Vitus Carbone that I built up last year has NOS sealed bearing everything on it (even the jockey wheels on the derailleur!), and I'm not the least worried of any of them wearing out anytime soon, if my 20+ year old Ofmega CX hubs on my other bike's clincher wheelset are an indication on how long they can last without one having to bother with them.
JMOs

Chombi