Taking Wigfish's solution even further...
Like he said, If you play for enough hours, it unlocks free play. As others have said, you can go into the pause menu instead of playing through or turboing
all night.
It's even easier. When the game starts, pause it and then pop out your battery pack.
The Xbox tells you to reconnect it, but you don't have to. Just go to sleep or work and when you come back, make sure you finish the game. (Kill yourself and then don't continue.) This is important; don't dashboard or it won't save your progress.
Also, Arcade and New Order don't stack for this. You have to idle-pause it twice to unlock free play.
Now that you have infinite continues, go ahead and finish the game. As others have noted, the difficulties don't stack. You have to play it three times for Arcade and three times for New Order.
Hope this helps!