Nothing destroys a business’s credibility faster than not delivering on a promise made to a customer. This can be at a brand level which is what we saw recently with Oxfam or at the proposition level.
If you offer same-day delivery but can’t realistically uphold that standard on a consistent basis, you're creating dissatisfied customers. Brands like Zappos realise this and rather than winning in the short run with big false promises they estimated their delivery time and doubled it promising delivery within five business days. The majority of orders are shipped overnight. This exceeds customers' expectations, making a positive impact and fostering trust in the brand.
Consumers may ask for quicker, faster, better but what delights them and keeps them returning is promises being kept.