Another Brake Actuator Question

I have a 2005 Prius with 56k miles. When I open the driver’s door I get a buzzing noise from the brake actuator that goes for about 10 seconds. Once the car is running the buzzing goes on for 5 seconds then off for about 8 seconds for as long as I drive. Any idea if this means imminent failure of the brake actuator? I see a lot of discussion about the brake actuator, but cannot find what is a “normal” amount of noise. A different thread stated that if the actuator is always on it will eventually burn out. Also - was this fixed in the 2008 and later models or is it something to expect if I buy another Prius? Thanks.