Max speed for wheel bearings I don't know much about bikes. I've got myself an older Specialized Stumpjumper. I asked myself the other day while I was riding with +50km/h through the forest what the maximum speed is the wheel bearings will endure and if there is e difference between smooth roads and trails.
50km/h = 13.9m/s = 833m/min. Wheel circumference is roughly 2m so that the wheel is spinning at 417rpm. Sealed industrial bearings easily withstand 10.000rpm and more. The steel ball bearings inside even more.