It's recommended to change the fluid each 30K miles. But can go up 50K easily. I saw ten year old cars with 180K and the fluid was never changed.
I've changed mine at 89K because by some reason it had some water in it.
You need to flush the power steering fluid on a 2003 Toyota Highlander every two to three years. You should check the fluid levels weekly.
every 30k miles
Not required
You should change your automatic transmission fluid in Toyota gearbox at least after every 30,000 miles.
ten thousand miles
50,000 mi
Urine because you can change the fluids often.
Read the owners manual. It has that information.
If your power steering pump makes a whining noise as you turn your steering wheel your power steering fluid reservoir is probably empty. The noise is caused when your power steering pump tries to pump fluid that is not there. This indicates that you probably have a leak somewhere in your power steering fluid lines. You can either try to find the leak or simply replace the power steering fluid every so often.
The transmission fluid on a Toyota Sienna should be changed every 100,000 miles. This helps to prolong the life of the transmission and improve performance.
Every 15,000 miles.
PS should be 18000 miles and brake fluid about 30000 miles PS should be 18000 miles and brake fluid about 30000 miles