There appears to be no pattern (mileage or time) to this issue but Nissan have upgraded the chain slippers and guides so they do recognise that there is an issue but will never admit it.
Although I have seen a few of these issues it is still quite rare and really my view is that you do not have a problem until you have a problem and no one should really be overly concerned about potential chain, slipper, guide or tensioner wear.
Alex.