When I book with Audi on demand, will I be able to choose to apply my rental days or are they automatically applied once my redemption code is redeemed? Can I save my rental days for a specific trip?

Once you redeem your Always Audi redemption code your credited rental days will automatically be applied to each Audi on demand rental until all credited rental days are used. There is no way to hold on to your credited rental days when booking a Audi on demand.