When you are planning a backyard graduation party, timing is everything. Ordering tents, tables, and chairs in early spring locks in the gear you need before the rush hits.
A typical setup runs about $1500. Spreading that cost out over time makes it much easier to handle alongside all the other expenses that pop up at the end of the school year.
Remember that the intro window is a strict deadline, not free money. If you still carry a balance when the 18 months are up, the remaining amount will start accruing interest.