There has been more than once where a package will fail to be delivered in a timely manner (the website indicates its been out for delivery for 5+ days), and they have always overnighted a replacement without charge or expectation that if the original shows up that I return it to them.

These missing packages have been primarily from when UPS/FedEx decides to use a last mile delivery service, instead of delivering it themselves, which is primarily staffed by low wage workers with frighteningly high turnover.