Under Armour Men's SpeedForm Gemini 3 Running Shoes

I was in need of a new pair of running shoes and was on my way to the Asics store to get a pair of their GT2000 or Kayano. I happened to have a UA Gift Card that I planned to use to get a couple of shirts or shorts. I'm glad I went to the UA store first and decided to REALLY check out your running shoes! After some consideration I decided on a pair of Speedform Gemini 3s. They fit and feel GREAT. The lacing system enables a consistent secure fit throughout my entire run. No having to stop and retie because the laces have loosened up. The Charged midsole supplies OUTSTANDING cushioning. I REALLY LIKE the way the heel of the upper is made and fits. The upper, insole and tongue are ALL very comfortable. Overall this is a VERY NICE SHOE THAT I HIGHLY RECOMMEND!!! My only concern is the way the High Abrasion rubber under the heel has worn. I've run approx. 400 miles in them and the rubber is worn thru almost to the midsole. Am I expecting too much or have they worn early?