What value a written constitution?

Constitutional change afoot?  Comments that NZ needs a four-year term for its governments have been appearing in the media since the last election.  Curious that our PM is making this suggestion when it was not promoted as Labour Party policy during the election.  No doubt it will be subject to debate, perhaps along with other constitutional changes.  The discussion on whether or not a written constitution is needed for NZ has been an enduring one with no conclusive result.  Some lessons can be drawn from the current debacle in the USA.  Despite have a very complex written constitution uncertainty abounds and conventions, developed over centuries are being tested.  Perhaps the best we can conclude is that a mix of both written constitution and convention is almost inevitable given it is clearly impossible to predict and prescribe human political behaviour.  How that mix is made up is the essence of the debate.