Hi Scotty - I have a 2019 Nissan Frontier 4.0 liter with automatic transmission. I only put about 7,000 miles on the truck annually. The oil gets changed twice a year but I'm not sure when I should change the other fluids. Transmission, Brake, or Coolant. Should it be done every so many years, because I don't put that many miles on it? Thank you
Have you checked your owners manual?
https://www.nissanusa.com/content/dam/Nissan/us/manuals-and-guides/frontier/2019/2019-Nissan-Frontier-owner-manual.pdf
General rule of thumb is every 30k but you don’t put that many miles I would do every 3 years if your not doing 30k in that time line
That manual in your glove compartment will tell you everything you need to know about your truck. Including fluid change intervals.