Some vehicles have long schedules between transmission fluid changes, while others recommend it every 3 years or so.
Some vehicles advertise “sealed for life” or “Lifetime Gearbox oil” but this needs to be read with caution. Inside a gearbox are multiple metal components that wear.
Leaving the worn microscopic pieces of metal floating about in the oil can only mean it is being run around your gearbox again and this can cause premature wear.
If you intend on keeping a car for more than the 3-6 years manufacturers want you to, then consider having your gearbox oil at the very least checked every once in a while.