sealed component reflexion part 2: BB

Think about a moving bicycle part that you almost never hear about. Not the crankset, it is just two pieces of metal. What impress me is the durability of sealed bottom brackets. They cost about 30$ for up to 5 years. There are 100% maintenance free and they are one of the most solicited part one a bicycle. Quite amazing. When the were loose bearing with cones, they were crappy unit. After they went to a cartridge form, they are one of the most durable part on a bike. How are they that good? Maybe because they are not sexy, so they don't have to be to light or underbuilt. Don't know. What I'm sure of is that every component should be as well designed.