What is the biggest advantage of using flat-rate boxes for shipping?

The most significant advantage of using flat-rate boxes for shipping lies in the fact that the cost remains consistent regardless of the weight of the contents, provided they fall within the specified weight limit. This means that customers can pack as much as they can fit in the box without worrying about incremental costs associated with heavier items. This pricing structure is advantageous for those who frequently ship heavier items, as it allows for predictable shipping costs, making it easier to budget for shipping expenses.

The option about the boxes being free may be misleading because while the boxes themselves do not have a cost, customers still need to pay for the shipping service. Faster delivery may depend on various factors, such as the type of service chosen or destination, and is not inherently guaranteed by using flat-rate boxes. The claim of unlimited weight is inaccurate as flat-rate boxes do come with a maximum weight limit, ensuring that they are still manageable for both the shipping service and the recipients.