Any brushed motor will wear out if run continously even if its loaded lightly. Even if windings are intact, if not the brushes then the commutators will wear - faster or slower depends on the thickness or materials used.
The only brushed motors that last long are the small tape motors simply because of light duty, light construction and not-so-continuous usage.
Even so I have come across tape motors that have commutators worn to the extent that the motor intermittently stops - only its belt coupling with the flywheel maintains rotation but at the cost of speed variations.
IMHO, the only motors that can run continuously are ones that do not use brusher - bldc, stepper, or induction. That's why ACs and fridges use induction motors in them.