Welcome back, Rebecca!
I'm happy to have the opportunity to be answering both of your fantastic Disney Dining Plan questions! When allocating how/when to use your dining credits (also known as entitlements), the platter of tasty planning is in your hands. If you choose to spend a day exploring outside "the world," your credits remain intact and available for you to use later that night, or the next day, or the day after that! You just need to make sure all your credits are used before they expire, which will be 11:59pm on the day of your departure.
My family loves to extend the magic as long as possible, so we always end up using our last dining credit for a departure day breakfast. Then, we head to our Resort hotel gift shop to redeem any unused snack credits for pre-packed food items, or, my favorite snack, Mickey Rice Krispie Treats - I bring them home to save for a day I need a little extra magic :)
Another tip: if for some reason you find yourself with leftover quick service credits that you won't have time to use, you can convert them into snacks! Yep - you can redeem one quick service meal for three snacks!
Before your vacation, don't forget to download the latest version of the
My Disney Experience Mobile App for your smartphone. One of its newest features include listing your Dining Plan credit balances. You'll be able to see how many credits have been redeemed, and how many credits you have left.
I hope to hear from you again, Rebecca! I also hope my answers have been useful in helping you plan a magical vacation while using a Disney Dining Plan.
Faith