When they list a change number it will be around 60K miles and then the transmissions still break when they want to. Nissan does not build reliable CVT until maybe the latest ones where they were forced to add some oldstyle standard ATX type features back to them to offload some of the CVT chain/pulley stress.
There is a software counter that the dealer resets when they change the fluid, it measures the amount of time the fluid has been run over a certain perceived 'danger' temperature and then they can diagnose whether to change the fluid early based on that number.
ALL car fluids can go bad with time, trans slower than engine but they still do. It is based on the hot/cold cycles and some of that occurs without the device even running as certain chemicals form once the fluids get used and then they change into other things worse with the time element even not being used. The worst one is water, which breathes in and out every day as water vapor through the breathers when the day temp goes up and down and then the water combines with certain fluid elements to make sludge acids which then eat metal parts.