I don't think there is anything wrong with trying to figure out what you can get away with. The only problem trying to figure it out is that you will most likely ruin your credit doing so. If your score drops many issuers will raise your APR based on that alone. You don't even have to be past due to get a default apr in some cases. So if you don't carry a balance, don't have any desires to get a mortgage or finance a car in the next 3 to 5 years. Then hack away at it. You ultimately have to ask yourself is the miles worth the cost of the damage to the report? That can also affect jobs and insurance premiums. Only you know the answer to this and no you can't fine tune IMHO. You can only look at what others have done and trial and error. But be warned, it can be hazardous to your score and ergo every thing else. If your score is not 800+, the game is not for you. YMMV