While it's best to serve the Frozen Strawberry Mint Julep immediately after blending to enjoy its slushy consistency, you can prepare some of the ingredients ahead of time to make the process quicker on the day of the party. For example, you can make the strawberry mint simple syrup up to a week in advance and store it in the refrigerator until you're ready to use it. You can also wash and chop the fresh mint and slice the limes in advance, storing them separately in airtight containers in the refrigerator until you're ready to use them. However, it's important to note that if you blend the cocktail mixture too far in advance, the slushy consistency may turn to liquid as the ice melts. So it's recommended to blend the cocktail mixture just before serving, or at most a couple of hours in advance and keep it in the freezer until ready to serve.