Reservations generally require a minimum of 5 hours.  Sometimes due to cancellations, short notice and shorter reserve times sometimes come available. You would get a message regarding this notification of availibility.  Maximum reservation length is typically 4 days in advance, but can vary based on vehicle availability. If you need a car more than 4 days, send an email to help@armadaenterprise.info and an account manager may be able to accommodate your driving needs.