You just sure as hell better pay it! It's not really a credit card per say. It's a charge card.
True, AMX is one that expects you to pay the complete balance every month so that is not costing you money (or at least not much). Of course most folks don’t do that.
On occasion, such as December when I decided to take an expensive vacation to Florida to treat my youngest Daughter and Son in law along with my Grandchildren to a rather costly Christmas trip to Disney World, I did not pay it all off at the normal monthly payment but let it roll over for 2 months and payed it off in installments along with a nominal interest fee (final payoff is next weekend per my schedule).
If you can manage your finances within reason, having this convenience is very useful, IMO.
I just buy everything on my American Express card and pay one bill a month. Groceries, gas, satellite TV, utilities, medical bills, insurance, you name it.
i do the same. one for personal and one for business.