Kris:
Do you wear down the shoe on the leg that gave out faster than the other leg?
I ran 7 this AM for 50 over the past 6 days. I'm content though tired. Tomorrow is a rest day for my last LSD before Baltimore... and then the MCM (Baltimore is going to be an LSD). I ran in my new Brooks today. When I bought the shoes, I told the guy how many miles I got out of the old pair (about 350) and that my left knee was starting to bother me. He said I should be getting another 100 or so but the knee should not be an issue. He suggested looking at my arches. He compared the two and noticed the left arch was notably different. This causes me to overcompensate on the left side and wear down that shoe faster. He fitted me for inserts. He even screwed up one and pulled out a brand new one and did it again (I never tried on the shoe - he put it in and it somehow didn't feel right). I think the service was good. It was also an analysis that I had not had before. Ultimately, these inserts should stop the foot movement in the shoe and promote stability up the leg.
I asked if such inserts would help with IT band issues and he said most definitely. Maybe you should take your discuss this with your running shoe doctor (e.g. not Foot Locker, righ Peach?), explain that you have an IT band issue and someone suggested inserts, etc.
The way the arches are measured is that you measure your foot with your foot relaxed. I'm just over a size eight- on the left foot -- but when I stand up, the foot size is almost 10. The right foot only has about a 1 size difference between resting and standing. Inserts cost about $35 and should last a year and a half.
My left knee had been bothering me over the past 10 days but felt great this AM... and even now when it's raining outside (often a problem).
Good luck.