I have no horse in this race, but common sense says it's all about communication. If a buyer pays a seller money, a reasonable expectation in my opinion (unless noted) is that the seller has the product on hand and can ship the product out within 24-72 hours.
If that is an issue, the seller should have the common courtesy to email or call the buyer about the delay. God forbid, the seller is really in an unfortunate situation, i.e. sickness, family matters, etc., and TRULY can't communicate to the buyer, ultimately their track record with customers will speak for itself.