An hour??? Wow!! I think thats about 59 minutes and 30 seconds too long
At club races-I cut the Comm, put in new brushes, seat them for about 30 seconds at 1 amp, pour Zubie drops all over them and run them about two runs, then recut comm and run one or two times more!! At a big race I do a very lengthy motor rebuild and break in, but even thats ONLY 3 minutes at 3 amps break in. I'll run the motor twice with a set of brushes and thats it!! At last years champs-I built motors for one run!!!
Those serrations are a good thing. I usually replace brushes when they are gone!!
Hope that helps.