For muffins, cupcakes, and cookies, the cooking time will shift by only a fraction. Start with an additional three minutes, then check for doneness every few minutes after that.
With cakes, you can use a slightly larger pan and check at the original time for doneness. After that, check every five minutes until the cake is baked through.
The bottom line is that there is no set time for doubling a recipe since it heavily depends on the contents and the pans or dishes you transfer them into.