any form of retargeting is only as good as the person and the campaign that is implemented as part of the follow up.
They visited you and didn't buy, but showed an interest. I would definitely start hard at trying to re-engage, and get them to buy at full price. I see too many people launch into a discount right off the bat, when the reason they didn't buy may not have been anything to do with price. If after you know they have seen further ads and not bought then offer a sequentially bigger discount to get them to buy, so it might be the same ad with the same message but with 10% off, then 20% and if they don't buy after a pre-determined period then stop retargeting them, they have moved on and so should you.