I used to have all my tires filled, now I have none of them filled. While we don't plan on having leaks or punctures, they happen. Then you have a mess. Depending on what's in the tires, you could end up with little dead spots whenever the tire rotated around. Don't forget to buy that special pressure gauge too, or that fluid will soon ruin the one you have. And when you do need to add a little air, don't overfill by a pound, or you might be letting some of that fluid out. Yes, some of these problems can be alleviated by making sure the valve stem is rotated to the top of the wheel. Yeah, that's handy, NOT.