I give it about a month.
Or 35 days at the most, according to one provider's website, until the KiwiSaver transfer process has completed.
Influenced, perhaps, by the general atmosphere of change new contribution rules and ownership upheavals (Tower, Axa etc) I decided to switch KiwiSaver providers.
And to make this dull administrative event sort of interesting, I'm doing a provider swap in competition with someone else: I've gone the paper-based route while my competitor has opted for an online removal service.
To be fair, the paper-oriented transfer had a bit of head start with the (duly authorised) documents in the mail at least 30 minutes before web transfer instructions were issued.