||First thing I did was to remove the grease it came with, made the bearings way too slow. Replaced the grease with speed cream, which works way better. My wheels spin for 1min+ now. They only downside I'm experiencing is that the bearings start to rattle after a while. I've been skating on them for a couple of weeks now, and the rattling is getting worse gradually. It doesn;t really decrease performance, the sound is just getting annoying.
Overall, decent bearings, if you're willing to put in the effort of actually maintaining them.