ORIGINAL: azalner
In the real world we use brushed motors all the time in industry. There is no such thing as ''breaking in'' a motor. When a motor fails we replace it with a new (rebuilt) one and put it into service immediately.
While you're right, every mechanical device that has physical contact points has a breakin period, whether you actually separate that from use or not. Engines, electric motors, shock absorbers, springs, etc. Everything has a breakin period.
Those of us who have been in the hobby long enough to remember paying $50+ for a good brushed motor will tell you that without a breakin, they don't last as long.