I understand there are millions of bikes that ride on loose ball bearings w/o problem. I think the major problem with these is that they are not sealed (that is they have no rubber seals) and I ride a lot. I am not willing to service bearings every other month. I had cheap wheels (<$100) with sealed bearings that lasted 15k+ miles w/o issue. I am specifically looking to change from loose balls to sealed cartridge bearings. I have learned this is not a common endeavor.