You hit a big goal, and a steakhouse dinner is the right way to mark it. The trick to keeping the celebration stress-free is handling the logistics well before you take your seat.
Book your table two weeks out to ensure you get a prime spot. Once the date is set, you can break down the $400 cost into manageable pieces rather than sweating the full amount the morning after.
The intro window is a deadline, not a gift. If you have a balance remaining after 18 months, the bank will start charging interest on whatever is left, which will make the dinner significantly more expensive.