Picture the yard dark, the projector humming, and the movie rolling while you sit outside with friends. Getting that setup together takes a bit of timing, especially since July is the sweet spot for outdoor gear sales when retailers clear out summer stock.
You want to map out your purchases before the sale hits so you are not scrambling. A little lead-time lets you hunt down the right screen and sound gear without paying full price.
That 0% window is a deadline, not free money. If you still have a balance left when the 18 months are up, standard interest kicks in on what is left over.