My first thought was, I should pre-pay for the next 9 years now to lock it in cheap... then I looked at the price I pay now, 15.88$ and I paid about 4$ initial registration.
Honestly there's no rush, it's a minor price increase, and I expect things to get more expensive as time flies anyway, that's what happens to literraly every subscription I pay (rent, watter, energy, council tax, internet, phone, email are all "subscriptions" I pay and all of them have increased in price, and will undoubtedly increase again). Not that there's anything you can do about it, it's the "cost of doing business".
I'll have to consider what's the lifetime of this domain, should I pay now, or am I going to throw it away in a few years/months for something else. I'll probably keep it as it's a good one, and I'll put an alarm for the 4th so I have enough time to think this through.
The `.io` price increase looks a bit bigger relatively speaking, but nothing earth shattering... so try following the same logic as I detailed above.
Now the question: how often do these increase?