Max Profit/Max Loss figures in risk profile for spreads are illusions. They don’t exist. The likely hood of your fly pinning to the exact penny is highly probable,
Don't you mean highly improbable?
And the OP may not know what you mean when you say "your fly pinning to the exact penny."
If they are still learning how a credit spread behaves, they may not know what a fly is, and they may not know what you mean by pinning.
With that being said, I agree that it is not common to actually realize the max profit or loss on a butterfly.
But I've done vertical spreads--both credit and debit spreads--that I have held through expiration. If both legs are far enough in the money, I sometimes just let the position dissolve on its own through assignment and exercise. And that will yield the max profit or loss. And it closes the position without any commissions (at most brokers).
BMK