The government might be dim and slow, but I guarantee you, they’ll be looking for ways to find, and punish, anyone doing this. Statistical analysis of driving distances and places of employment, for instance, would catch most cheaters. Comparison of odometer readings upon registration renewal against tax records would be another… I can come up with two or three other counter-measures just off the top of my head, if you want them. A very few might be smart, lucky, and industrious enough to cheat the system in this way, but they’ll be few and far between.