In 1992, my then seventy-six year old mother came back from a three-week trip to Italy. “That”, she said, “is my last big trip”.

Mum had been an avid traveller, but I knew she really meant that this was the end of her overseas adventures. The post cards and letters I’d received were full of the travails of travel – plumbing that didn’t work, taxis overcharging, dodgy food. She believed she’d had a hard time of it.

However, it wasn’t like she’d had a particularly bad run of service in Rome or Florence, nor on the way through in Singapore. I’d received plenty of missives complaining about this and that while she was on previous trips – but this one seemed different.

And it was different – now she was 76. Everything was starting to irritate and tire her much more than before, and she found all the mundane little requirements of travel harder. Mum was in good shape – she lived to 97 – but she just couldn’t quite hack it anymore and, most important, it was no longer fun. Things had changed: she was getting older and she just wanted to be home where everything was familiar. She never left New Zealand again.

My mother lived out her retirement happily and from this point her expenditure gradually fell. This reduction in spending during retirement has been well recognised and studied and is really quite understandable: as you get older activities like travel become more difficult and less enjoyable, so you do them less. And therefore your costs generally fall.

Although it may seem unsettling for a new retiree to spend more in the early years of retirement, it’s what you should do – you can be pretty sure that this higher expenditure early on will be made up for later when spending drops away.

Of course, life can throw a few curveballs from time to time in the form of unexpected costs with the potential to blow retirement plans out of the water!

On this, Sudipto Banerjee, a retirement thought leader at T Rowe Price (a major US investment firm), has scoured data from various sources and come up with some interesting findings.

The important one for me is the number of retirees for whom expenses rose significantly: 50% of retirees experienced up to a 25% increase in their expenditure. Worse, 28% of retirees experienced a 25%-50% hike in expenses, while 21% had a spending increase of 50%-100%.

This suggests a substantial number of retirees are receiving some kind of serious shock to their finances.

My mother’s expenditure fell as she settled into a more sedentary life. And Banerjee’s findings show that there is indeed an on-average fall in expenditure (about 2% a year) in retirement. However, that decline is not steady; many retirees experience meaningful variations in spending, including some sudden increases.

Importantly, these rising expenses were mostly for non-discretionary spending – essential items, in other words, mainly relating to housing, health or transport.

Of the three, housing was the greatest expense, even when people rented. Renters could be hit with sudden rent rises, while owners could uncover major maintenance needs.

Many Kiwi homeowners could face further sharp increases in rates and insurance in the coming years, and for some, such increases might not be one-offs. It’s likely that many retirees will have to adapt to ongoing rates increases.