I can go 4.5 hours into a 25 mph wind pedalling myself, at 6 mph. I have an old fashioned cushioned wide seat, not one of those splinters the bike shops stock exclusively. I buy seats at Salvation Army. Fighting that much wind wears me out, but I gotta go to/from my summer camp when city services and appointments allow me.
So electrically driven, at 15 mph, I could easily make 72 miles. I bought a 15 AH 48 v battery, because I have a couple of fall parties and concerts I'd like to attend that are 35-40 miles away. I'm not counting on finding a charger at the destination; I'm sure one is not available at the one I attended in October (by rental car).
As an added bonus, electrical drive could fight the wind for me, getting me there on my normal commute in a normal 3.5 hr. I don't intend to use it on nice days. 3.5 hour exercise twice a week has been good for my cardiovascular system. I'm age 67.
So far my endurance greatly exceeds that of the motor/controller I bought, which lasted about 80 miles. I pedalled it to destination from two failures