Man, it really depends on what your goals are. If you like riding and are not interested in racing than what is wrong with 25kph? Seriously. If you want to race, that is another story. You are active and that is great. If you want to train for an event, determine what your goals for the event are, then plan your training.

Also, many BF posters are full of crap: some people are faster, some are slower, some lie about being faster and some hate anything about what one's "average speed" ought to be. I say it ought to be whatever makes you feel good and proud of yourself. Very very few of us are pro (not me).

Good luck!