I currently use 2 pairs of running shoes, one that's more rigid for long runs and long workouts and a slightly more minimalist pair for speedwork and easy days. I am a neutral runner and have had no injury problems in the past year. I also run about 40 miles a week. I recently picked up a pair of shoes similar to the more rigid one I currently use, as well as the Saucony Kinvara 3s. I was wondering if I could use the Kinvara 3s for ALL of my runs, not just speedwork and easy runs? Long runs are usually about 6-8 miles and long workouts are about 6-9 miles. Would the Kinvara 3s be able to hold up and perform well even on the longer runs?