I do wheel bearing failure analysis for a living. I just wanted to add that typically a wheel bearing fails because of poor sealing - allowing contaminants and water in, and grease out - which seriously degrades lubrication of the bearing and leads to failure. During bearing service, the seal MUST be replaced and not damaged in the process. This is much more important than the type of grease being used, as long as it's a hi-temp grease made for wheel bearing application.
95 E320 Cabriolet, 131K