How often do you trade out your running shoes? Are you diligent or do you let it slide?
While it's important to make sure to get new ones on a regular basis, research has also shown that running in several slightly different pair at the same time is beneficial and can reduce injury.
While the initial investment may cause you to hesitate, the investment in PT and frustration in backing off training due to injury could be worse.
Jim Wnorowski of Endurance House Westminste has some great information and helpful advise.