How long would you cook chicken meatballs so they are perfectly done?

Here's a recipe that sounds somewhat similar to what you're trying to do that calls for baking 35 minutes @ 350: http://food52.com/recipes/23522-baked-turkey-quinoa-spinach-meatballs
"Perfection," though, will depend just as much on the prep as the cooking; hopefully you've incorporated some kind of fat if you're using 90% lean meat or leaner, and that the ingredients haven't been over mixed. Both can lead to dry or tough meatballs.