Well, the good news is, here in N. America at least (don't know about New Zealand, kiwiME...), Kia & Hyundai have a long 10 year / 100,000 mile (160,000 km) in case the gearbox starts making strange noises.
@KIwiME , Could it be possible Kia-Hyundai did not harden the gear wear surfaces and/or bearings in there enough? Lack of proper carbonitriding has caused a Ford Focus EV gearbox recall in my own experience, and I've heard of that problem popping up on some (VW?) cam surfaces in valvetrains.
Its easy to change the fluid on a Leaf, so I can do it just for fun at home really.
I will sort of copy what Hyundai-Kia specs with their GL-4 70W/75W at about 6 cSt (Mine will be Redline MT-LV all-POA at a similar 6.5 cSt kv100). GL-4 has more phosphorus for anti-wear than ATF (Matic S, Dex VI, etc) fluid does.
2022 Leaf SV+
2020 Leaf SV - sold
2022 Maverick Hybrid
2016 Ford Focus Electric (traded in at 34k miles, 5 years)
& Some really junky gasoline vehicles, not green, except for a Ford C-Max Hybrid, nice one.