10 mph all things counted is a good ballpark figure for most people. Make it 9 if you think you are slow. So if you want to be on the road for 6 hours a day, you could aim for 60 miles. If you want to make more miles in a day, it is much much easier to add extra mileage by just biking for longer rather than biking faster if that makes any sense. 30 minutes isn't a whole lot of time out of your day, and at a moderate pace it doesn't take a lot of effort to bike for 30 minutes at the end of the day, but it can easily add 5 miles more to your daily distance.