If it is a distance that you have set for a exercise program then I would say if the total was 100, or whatever, you would need to divide it up per day or every other day as to get the best benefits. Doing it all in one day would not be as beneficial as say every day or every other day. Like weight lifting. you wouldn't lift x amount of weight all in one session and rest the other 6 days.

So for me if you are doing biking for exercise then ride as often as you can and do not worry about a total mileage per week, just ride.