I've been running in the Brooks ST and have a little over 500 miles on them. There is signifigant wear on the outside part of my insoles (more so on the right)and was wondering if I should retire them. The thing is they still feel really good and fit my feet well. I just got another pair and they feel bulky and stiff. Do I just need a break-in period, or should I just run in my older ST's until they explode? I'm a pretty effiecient, lightweight forefoot runner so I tend to get more mileage out of lightweight trainers than most.