Facing is a big fat con :twisted:
There will be others who swear by it, but I've never had it done and have HTII bottom brackets that are 4+ years old - they have been regularly serviced though............and there lies the crux of the matter.
I think when BBs fail the manufacturer will say, "well you didn't have it faced, that's the problem." When really it all boils down to HTII BBs being outside the frame, and therefore more liable to dirt/water ingress.