Have pulled out more than one spare tire that had little or no air in it, none of the spares were mine. For my own i try to check every six months or so, which reminds me that i am due. Even had a flat tire the other day on the car with no spare, and it comes from the factory with no spare tire. Luckily i was at home so i just changed cars, fixed it later when i got back from work. All of the vehicles have a bottle of slime with a small air compressor and i also carry an industrial grade plug kit and that is one of the things i move to the vehicle i am driving that day.