Consumers show a clear preference for a guaranteed reward as the certainty of the reward forms part of the overall value equation in the consumer’s mind. Essentially:
The closer the reward to the point of purchase + the lower the amount of effort required by the consumer = the greater the likely impact.
This is what makes Gift with Purchase promotions so compelling to consumers. For a guaranteed Gift with Purchase, you can also forgo the full terms and conditions, and instead only have abridged terms and conditions on all promotional advertising which outline the key conditions of the offer.