I never said bitcoins grew exponentially, how can they there will only ever be 21 million of them.
I do understand what exponential growth is (that's why I recommend looking at Dr Bartletts videos)!
You are absolutely right it is not sustainable that is the point I'm making in part. Unless we have sudden depopulation then goods and services will need to grow to match a growing population and in doing so the money supply has to grow to match the goods and services that the people want. Splitting a currency is the same as devaluing a currency the only way it can work is for the goods and services to value from what they were previously. Imagine you have a product it cast you 100 bitcoins to make 6 months later you can only sell it for 75 bitcoins that's defaltion.