in the winter, realistically once a week. My GF lives in philly, so I spend the weekends there usually. Conveniently, her apt. is 2 blocks away from the trailhead at wissahickon and I can make it down to the trails in DE in less than an hour. I do a few trainer nights a week too.
In the summer, I try to be on one of my bikes every day, with serious rides at least 3 days of the week.