Hi Kristin, and welcome back to the Disney Parks Moms Panel!
I would be pleased to help you out with your question, as not only am I someone who frequently books "split-stay" vacations at two (or more)
Walt Disney World Resort hotels during a single trip, but I am also a huge fan of the Disney Resort refillable mugs and typically pick one up most trips.
Disney Resort refillable mugs can be used at any Disney Resort hotel, and will be valid for your length of stay (up to 14 consecutive calendar days), even if your visit encompasses two different Walt Disney World Resort hotels. Therefore, provided your vacation does not exceed 14 days, you will definitely be able to use your mug at both Resort hotels.
At the end of your trip, don't forget to bring your mugs home. They make great souvenirs! At my house, we have a whole cupboard drawer filled with our Disney mugs, and generally use them during family movie nights or whenever we feel the need for a little extra Disney magic in our day.
Kristin, I hope this information is helpful as you continue to finalize plans for your trip. Should you have any other questions, please be sure to let us know. We would love to hEAR from you again!
Wishing you a Magical upcoming Disney vacation!
Trish