LoadLevelAsync multiple pending scenes?

I'm trying to create a system that loads the main menu and the next scene in the background. I want this because I don't want the user to wait a long time for the level to load after pressing "next level". Here is what I have so far:

 private AsyncOperation nextLevel;
 private AsyncOperation mainMenu;
 
 void Start () {
     nextLevel = Application.LoadLevelAsync (Application.loadedLevel + 1);
     nextLevel.allowSceneActivation = false;
 
     mainMenu = Application.LoadLevelAsync (0);
     mainMenu.allowSceneActivation = false;
 }
 
 public void goToNextLevel () {
     nextLevel.allowSceneActivation = true;
     }
 
 public void goToMainMenu () {
     mainMenu.allowSceneActivation = true;
 }

As you can see, I define 2 AsyncOperations for 2 scenes. I then allow scene activation later in different functions. When I call goToMainMenu() nothing happens. How can I load multiple scenes in the background but not switch to them unless the user calls a function?

Application.LoadLevel("scene") takes a long time for large scenes. I want to load the next scene in the background so that the switch can happen instantly. Imagine a simple pac-man game. Would you really want to wait a few seconds after each level?