For easy lube and standard lube the hub is the place to monitor temps.
For Nev-R-Lube Dexter hubs with disc brakes I have found the place to monitor for temps is the rotor braking surface. The hub seems to stay quite cool vs the rotor when in the early stages of bearing failure.
Because the inner & outer races are quite close together the angle of the disc from vertical is more extreme for a similar amount of bearing wear. This causes the disc to cant within the pad area and generate heat.
Any hub temperature increase will most likely come as a result of propagation from the rotor with metal to metal contact between the disc and caliper flange coming in the later stages of failure. I have seen temps in the 375° range once this commences.
