When changing recipe size, do I proportionally change bake time?
Baking times are based on the size of what's in the oven. If making 1, 3, 6, 12, 24 or 48 cupcakes of the same size, you bake them the same time, as each one "sees" the oven the same way or has the same volume/thickness from the outside where the heat is to the center.

If making mini-cupcakes or giant cupcakes, or baking a cake using a cupcake recipe, the baking time needs to change with the size of what goes into the oven full of batter, as there is more or less batter to be cooked through from the outside edge and bottom/top of the pan.