Fair enough. It seems to me that if an application has high performance demands and is expected to be in service for years, it should eventually be rewritten in a faster language. I find myself designing/developing programs in Python because development is so fast, then rewriting the result in a faster language after the design phase is over.

The rewriting phase is basically a translation, not a redesign. In most cases I know exactly how the program should behave, so there's no design taking place.