As a rule, a CTE will NEVER improve performance. A CTE is essentially a disposable view. There are no additional statistics stored, no indexes, etc. It functions as a shorthand for a subquery. In my opinion they can be EASILY overused (I see a lot of overuse in code in my job).
Check the cupcakes at the minimum baking time. If the recommended baking time is 18-22 minutes, check them at 17 or 18 minutes (just a quick peek, make sure not to let too much heat out of the oven). If the tops are rounded and no long appear wet, they may be done.
Cupcakes made from a butter base may keep for up to three days when left sitting on the counter or at room temperature. Heavier cakes, including chocolate and vanilla, also keep for up to three days. Cakes that have more moistness, including dulce de leche and caramel cupcakes, should last for up to five days.