I remember watching a video interview with Rupp and he said he has been wearing Nike Structure's since they we initially released a number of years ago.
As far as the 4 days a week philosophy I actually don't think that's too crazy of a statement. Obviously, this assumes the 4 days a week you are running are your harder days, which is a common number of workout/longer steady run days for someone seriously training. The 3 easy days in a week of training really aren't developing much as far as fitness. Unless you are a competitive runner that 10% doesn't mean much. (This would be an interesting experiment to try; the difference in performance for say a 5k or 10k based on a training cycle of 4 moderate/hard days a week with the other 3 being completely off versus 4 moderate/hard days a week with the other 3 days each week being easy).