No to mention that it is also not compliant with the code, even at 60C (55A max at 60C).Please don't say things like this as it is completely wrong. If the circuit is installed as Rocky described above, it is perfectly safe and meets all of the electrical code requirements.
To answer the real question, yes, you can put in the circuit that is capable of 60A and run it at only 50A either by configuring the connector or the car. However, you are doing it for your own peace of mind. It will not help the battery by running at 50A vs. 60A. It really doesn't care.
I agree the battery life thing is probably not a factor, especially compared to SC.