If you held the spread to expiration and both calls expired in the money, you would realize the max amount of 5 for you spread. Since you paid 2.55 for it, you would make 2.45. ($245).
The risk of holding through expiration is your short side finishes just out of the money and you come in long stock when your long calls are exercised. Even if both are in the money, there is a chance your short calls are not exercised and you come in long stock.
Some brokers will sell out your position on expiration day if you don't have the money to cover the exercise.
This is why I would suggest selling to close your spread before the end of expiration day.