Good plan, but some customers will still complain. It's all part of selling at this time of year. You make more money and people are more impatient. I feel it's a worthwhile tradeoff, and if I get an unjust neg or neu, so be it.
Here's an insider tip: Priority Mail items really do have higher priority when it comes to them being shipped and received once you mail them. Mail clerks can hold Parcel Post items for days (almost always on Mondays in December), while Priority are the first ones given to the carriers to deliver. So if you want your items to arrive with the best chance of being on time, use Priority.
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Sick From Prilosec