I don't want to argue pointlessly, but while your conclusion may be right, I think your logic makes some leaps. Why is day the natural time scale? No one needs a plane every hour and no one needs a car every hour either. By that time scale, they are the same. Also, everyone needs a plane every year and needs a car every year too. On that time scale they are also the same. Only in a cherry-picked intermediate time scale are they different. :) I think your answer would be improved if you could justify why the daily time scale is most relevant.