Autoslash does have a generous free cancellation option on their pre-payment offers that they occasionally include in their quotes, unfortunately I often find other vendors who offer pre-payment rates that are cheaper--of course for those they are almost always non-cancellable, no refund. Nevertheless, I do occasionally use the latter, but only as follows: I book the best "pay at pickup" rate that I can find (including a pre-pay through Autoslash), and then I wait until 1-3 days before my pickup time, and only then, I check for pre-pay rates that are non-cancellable (like the express rates on Priceline, or on any of the major rental car sites). By ONLY booking those non-cancellable bookings a day or a couple of days before my pickup, I've reduced my risk substantially. And of course if there are no pre-pay rates that beat my original reservation, at least I covered that option. I should add, I only do pre-pay bookings with the major rental car companies. I don't do pre-pay very often, but occasionally I find some great last minute pre-pay rates and by only doing it a day or a couple of days before my need, I have substantially reduced my risk versus booking a prepay weeks or months in advance, which of course I would never do (other than through Autoslash).