I know exactly what you mean. And to a point, I still feel that way after two years of a 30-mile round trip bike commute. I try to do the commute 3 days per week. Any more than that, and it just feels too much like hard work instead of play time. 3 days of bike commuting allows me to get in one day of cycling on the weekends, usually a 10 or 15 mile trip with my daughter on the trailer bike.