The Tamiya 70168 double gearbox comes with 2 FA-130 Mabuchi motors, rated 12000 at 3V, aprox.
Those motors seem to have a short life, even running at that voltage level.
There are a lot of “S” can Mabuchi motor types used in scalextric, which fit in the gearbox (same can as that of the FA-130).
Rated at different RPM (normally specified for 12V), they’re designed for lasting longer. Another requisite refers to the shaft, it has to be 2mm wide to accept the gearbox pinion:
professormotor.com/cat_motors.shtml
according to Mabuchi, there’s another motor, the FC-130 rated for 6V and suitable for radiocontrol, so I GUESS it comes with carbon brushes, not metal, so less sparking (anyway capacitors are needed for RC applications) and longer life.
Robert