It all depends on what kind of life the pads have had, and how much material is left on the pad. The thinner the pad the harder it can loose the heat. I'm sure when we checked the outer pads they seemed not too bad, but again many factors could be at play here.
Black stuff below is slightly better than OEM. I would deffo change the brake fluid anyway, for peace of mind, but it could do with testing to see if the boiling point has been effected, or of there is any water content because its Hygroscopic it can pick up moisture over time, usually recommended to be replaced every two years. Just depends on driving styles and all that jazz.