You may think that your tires are supporting your vehicle. But actually, it's the air pressure inside your tires that's providing support. That's why it's so important to check your tire pressure regularly to ensure the best handling, traction, and durability.
Just like a balloon that starts to lose air after a few days, tire pressure changes over time. Even though tires are fairly airtight, there are still microscopic pores in the tire walls that let very small amounts of air escape over time. This is called permeation.
Generally speaking, even if there's no other air loss (like a puncture or pinhole leak), a tire inflated between 30-35 psi (pounds per square inch) will lose approximately 1 psi per month. So if you don't add air for a few months, your tires could be 2-3 psi under-inflated. While that may not seem like much, it's definitely enough to make a difference in handling, safety, and tire wear.
The best thing you can do for your tires is to check the tire inflation pressure every month. This will help your tires reach their optimal traction, stability, and durability. Also, once you start checking regularly, it'll be easier to notice if you have additional leakage due to a puncture or other small leak -- and it's always better to detect a problem early before the tire is damaged due to excessively low pressure.