Actual range of the battery

As I wait for My Revenant I wonder what is the actual range on the Prime or if you have a Revenant what is true range you can get out of it on a single full charge? I am use to riding a normal bike 50-100 miles at a time. I know I won't get close to 100 miles on a charge but just curious. Also would it be smart to buy a second battery as a back up?