I don't have a BMX, but I ride road and mtb's.
Mtb is a bit random, sort of as and when I feel like it or when there is an event I fancy.
Road, I try to get out every other days, after work, and distance can be anywhere between 25 and 60 k depending on how much time I have.
According to my Garmin (that I take on most rides), I am managing around 300k per month, starting at the beginning of February. But, as the weather improves, I'm certain the distances will go up.