To be honest, a 2011 Prius will probably suffer from headgasket failure or HV battery pack failure (in that order) before the brake fluid becomes an issue. If you are nearing 150K, either or both of those items will probably bite you sooner or later.
The brake actuator issues, while it does happen, are not that common. You're more likely to have an issue with the pads seizing in the caliper brackets from rust.