The recommended frequency for checking and changing power steering fluid, brake fluid, and coolant can vary depending on the make and model of your car. Generally, it's a good idea to refer to your car's owner manual for specific recommendations from the manufacturer.
In general, it's recommended to check the power steering fluid and brake fluid every 30,000 miles or 2 years, whichever comes first. Coolant should be checked at least once a year, and changed every 2-5 years depending on the type of coolant and your car's manufacturer recommendations.
It's important to note that if you notice any issues with your power steering, brakes, or cooling system, such as leaks, strange noises or smells, or overheating, you should have your car inspected by a mechanic as soon as possible.