Tim and Kathriona live in Sharon Place, Awapuni, and change their flag about once a week.
They receive a lot of comments – not just from neighbours but dog walkers and other passersby. A woman knocked on their door one day to say they were flying "her" flag – the three-legged man of the Isle of Man.
Their Zimbabwean-born neighbour got excited when they flew that country's flag.
"You never know who we are going to impress or affect," Kathriona says.
Tim and Kathriona bought many of their flags during their travels. Most are country, island or city ones but they also have novelty ones such as Blackbeard the pirate's personal flag that features a skeleton.
Another flag is a parrot eyeing up a cocktail and proclaiming "it's five o'clock somewhere".
They also have a collection of event-specific flags, such as Happy New Year and Happy Easter.
Friends and family know to buy them flags. The spreadsheet comes in handy as they often go into a shop and forget they already have a particular flag.