What is TOO big for a ball python terrarium?

[Fraido]

False. There is such a thing as too big. That results in you having to buy unnecessary things to make the cage cluttered, or purchasing additional hides. Not to mention it requires more bedding unless you use newspaper/paper towels. Also with more cage clutter comes more cleaning.

Just 'cuz it is more costly, and requires more work, doesn't make it false Neal!

My opinion; there's no such thing as too big if you're able to make it work. (More clutter, can clean it all properly, etc.)