IMO keeping brake fluid relatively fresh has as much or more to do with maximizing brake system component life as it does stopping power.
Being somewhat lazy when it comes to that, I’ve never straight bled all the old fluid out which is the best method. But I use the replacement method. When fluid looks pretty dirty, I’ll replace the fluid in the master cyl. Several times over the course of weeks or months. The new mixes with the old after driving for a while, but is a bit cleaner. After several replacements it’s not perfect, but better. Same concept as drain and fill on a transmission vs fluid replacement method.
But If you have a couple hours to kill, bleeding it out is the best way.