This is what I do for all my vehicles and recommend to everyone. I also drive my vehicles hard, so if you don't you can stretch these out an extra 10 or 20K miles. There is no such thing as a lifetime fluid, all oils break down over time and use reducing their ability to lubricate.
Front diff every 30k miles or 2 years.
Transfer case every 30k miles or 2 years.
Rear diff every 30k miles or 2 years.
Transmission every 30k miles or 2 years.
Brake fluid every 30k miles or 2 years.
Engine coolant every 30k miles or 2 years
I know this seems excessive but if changing the fluids regularly keep my truck from being on the side of the road and have to spend a thousands on new parts then its worth it to me.