You should feel lucky you can get out that much and stay in top shape but not everyone can.
a lot of people will find this harsh, but the time excuse is the one i hear the most - there really is no excuse for not being reasonably fit. of couse i'm not going to include people who are ill with cancer or some other disease/affliction, but the whole 'i don't have enough time thing' is just a bs excuse to keep one's ass parked. sure i may get labeled a fitness nazi because of it, so be it.
the funny thing is that i am not super fit, i don't go out and run a marathon each week, and i don't have sub 10% bodyfat, but i do perscibe to maintaining what i believe to be a minimum standard or decent level of fitness. and that standard is not extremely high, it is something that is achievable by nearly everyone. i train a woman who has cerebral palsy and is in a wheelchair, but she comes in to exercise on a regular basis and does what she can to maintain and improve her health.
nobody is so busy that on 4 out of 7 days per week they couldn't find 10-15 minutes two times over the course of the day to do some exercise. if you can't you're just lying to yourself.
with my rant over, i would say that walking your bike up fromme is getting some exercise.
We don't know what our limits are, so to start something with the idea of being limited actually ends up limiting us.
Ellen Langer