How often are you supposed to replace and rotate the tires? The bike only has about 900 miles on it. The tires appearred to still be in good shape. I didn't realize they should be rotated but that makes perfect sense. I have never even had a flat on it. So my first incident I have to replace the entire tire

It is funny because I was not really sure why I decided to slow down and stop. My mother is convinced I have a "bike angel" who was looking out for me.