If you remember them, they'll do a better job of remembering you. And that means better mail delivery. Ask at your post office. Your postman doesn't work every day, he gets days off from time to time. When that happens your mail is delivered by a substitute.
Substitutes are notorious, everywhere, for poor delivery of packages.
Believing the package lost, I had already replaced it. One missing package, destined for France, was recently returned after nearly two months. Couldn't understand why. The address was clear, the customs form was made out, there was postage on the package. Whether by surface or air, books ship at a special discount rate.