I need a Hertz car on a Friday, from 8AM to 8PM. My UA 50% off car coupon says that it requires a Friday or Saturday overnight keep. My question is whether it's ok if I have a reservation from Friday 8AM until Saturday 8AM, but actually return the car Friday night -- will my coupon still apply?

The person at the Hertz Gold desk basically told me "no way" -- if I don't physically hold the car overnight Friday night, the coupon doesn't apply. I'm not sure whether this is true.

Can anyone help? Thanks in advance!