Oh wait, I misread your original comment and thought you were talking about regular cars. These DIY electric cars, do they run on batteries? If so, what type?

Regarding the diode theory, it might have some merit if the bulb was connected to an alternating current (AC) circuit, which most electric grids run on. The diode would only allow 1 phase of the AC to pass through and filter out the opposite phase, causing the bulb to turn on and off very quickly. For North American grids where we run 60Hz AC, that's about 8.3ms (1/60/2=0.0083) on and 8.3ms off; fast enough for the naked eye to not notice the flicker. As such, it keeps the bulb off for half of the time than if it was full AC passing through it, which might reduce the amount of heat produced and might help prolong the bulb's lifespan. Again, just pure theory, have not tested it, so I might be wrong.

But if those DIY electric cars run on DC batteries, I really don't see how adding a diode to the circuit would help prolong the lifespan of the bulb, whether it's tungsten bulb or not.