Indefinitely, well, that sounds pretty long to me. A lot longer than the up until one-hundred years ago when your forefathers still hunted down Indians to make space for the new free roaming capitalist empire. We will see adjustments down the road, I very much hope so at least and expect such, but I would venture to bet that the Euro itself will outlive you, Tsingtao 

To answer as simply as possible, a varying degree of economies and strengths cannot have one monetary policy addressing all. Not indefinitely, at least.