At the time Key passed the edict in 2009, the release of expenses was still new and Key was under fire because National had racked up $739,000 in international travel in its first three months in office - more than double the amount Labour spent in the same period the year before.
In newly released ministerial expenses from October to December last year those costs were over the $1 million mark, although lower than the high of $1.2 million for the quarter before that.
Key walked the talk by paying for Bronagh and his childrens' airfares out of his own pocket - but he could afford to.
That could have created a rod for his successors' backs - although it is expected Prime Ministers will take their partners or spouses on official overseas travel where they can be an important part of oiling the wheels of diplomacy.
Australian PM Malcolm Turnbull's wife Lucy came on his visit to Queenstown last week and the Turnbulls and Englishes went out for dinner and a walk.