First up is the misunderstanding of a "sealed" bearing. Many people think sealed means the bearing is permanently sealed, both from contamination and from needed maintenance. This is not true. While some low end bearings come with metal shields making removal a difficult process, most quality bearings come with rubber seals often referred to as "2RS". This stands for 2 rubber seals.
Our VCRC Ceramic bearings use rubber seals which can easily be removed for servicing (greasing and if needed, cleaning) and reinstalled.
This is also true for steel bearings that use rubber seals. Don't think that just because they are "sealed" it means they don't need maintenance. Bearings are like chains, you need to keep them lubed and clean for them to last. A VCRC Ceramic bearing will last longer than steel when properly maintained as the parts don't wear as easily as steel, but the longevity has a lot to do with proper maintenance.