One of the best ways to prolong the life of your shoes and prevent yourself from getting injured is to rotate your shoes between every run.
You should always try to keep at least two active pairs of running shoes available, if not three or four pairs. Whenever possible, you should avoid running in the same pair of shoes more than once a day, and would preferably not wear the same shoes two days in a row.
When you run in a pair of shoes, even on a warm or cool day with no precipitation and a dry surface, your shoes still get a little wet. Your feet sweat, and the fabric can absorb some of the humidity from the air. By not wearing your shoes two days in a row, you will allow your shoes to completely dry out.
Not wearing the same shoes two days in a row also means that the rubber in the sole of the shoe will have an opportunity to decompress before you wear them again. You are applying a lot of force with each foot strike, and the materials in the sole of the shoe will get a tiny bit denser and take a little bit of time to go back to it’s normal state. If you never allow it to completely get back to it’s normal uncompressed state, then it’s normal state will begin to default to being a little compressed.
Rotating your running shoes will extend the life of your shoes. Not only will your shoes last twice as long on the calendar because you are only wearing them half as often (or less), but they will last a little more in terms of the mileage you can run in them because you are taking better care of them.
Using a different pair of shoes each day is better for your feet as well. You have a better chance of avoiding the start of a run with wet feet, and your feet will not have the exact same cushioning and padding for each run. Doing the exact same thing day in and day out can be detrimental to your body in any type of exercise and lead to overuse injuries, so changing things up on a regular basis will help develop your muscles and support a little better.
You can wear the same style of shoe and just rotate between pairs, or you can really change things up and have different styles and makes of shoes that you wear from day to day. You may even want to consider different shoes for different circumstances, such as trainers for normal workouts, racing flats for speedwork and races, and trail shoes for when you get off of the roads.