I like these - not the cheapest but I get really good life out of these. I go through a set of belts and drive bearings about every 6 months. Bearings about every 12.
I ride about 200km a week so I get between 5 and 10,000km out of my bearings (I never ride in the wet)
Expensive but worth it.
Evolve creamic bearings
Like butter, very very smooth.