There is a pricing option which allows you to "Only charge for featured ads" (essentially all listings are free unless the customer selects the "featured" option), and you need to create at least one ad pack for this. The duration of the featured ad is the same as what is set in the ad pack, but it is a set price for all featured ads, so whilst you could create multiple ad packs for various durations, the actual price for featuring the ad would be the same for all of them. So ultimately it's not possible to set it up exactly as you describe in terms of a different price for each featured ad duration (at least not without customization of the default theme).Thanks.
