I agree with Maddog, a lot of folks have more than the 150 hours on their birds. I would think the failure on brushless motors is either temperature related or bearings (or the ESC that drives them). Not sure what evidence temp related failure would provide but bearings on the other hand usually make different noise when they start to fail. Bearings can be monitored/replaced with better ones, and even lubed.
Brushless motors were designed for reliability. Personally I think the ESC would fail since it has the electronic components and again this I suspect would be related to temperature induced failures. If you keep your props balanced, keep your bird/motors out of dusty/dirty/sandy conditions, and check sound of motor, spin the shaft in your fingers (compare one motor to the others) to feel any roughness or difference, it would go a long way to get the most out of them. I have flown brushless motors on my R/C planes for a quite a few years and I haven't had any failures there and none on my Solos yet.