If it works, question it
There are many assumptions that went into your design development, among them that the drop height likely to be encountered is realistic, and that the fragility value used is representative of the product actually being packaged. Even when you are lucky enough to be working with a fragility value that was obtained by actual testing, in many cases what was tested was a prototype, and the production units may be more or less rugged than indicated.
For these reasons, it is a good practice to monitor the performance of your design in actual use. This will help you to determine if your design is providing more real-world performance than is actually required, or not enough. It can also allow you to determine when internal changes in the design of the packaged product might alter the requirements for package performance.
Just as no shipper can afford high damage rates, neither can he afford to overpackage. Monitoring of packaging performance on an ongoing basis can also help determine if further economies can be achieved without sacrificing protection.