Can I use it for an event that runs more than one day?

Yes: an event accepts uploads until it expires, so a wedding weekend or a company off-site can run on one QR code as long as the whole stretch fits inside the storage window.

The window counts from the day you create the event, not from the first day of the event. A free event lasts 14 days, which covers a weekend comfortably if you create it in the same week. A paid event lasts 12 months from the upgrade, so it can be created months ahead and stay open long after the last day for guests who upload late.

There is no per-day limit, only the per-guest limit of the plan: 20 photos per guest on the free plan, unlimited photos and videos on the paid plan. The same QR code and link work on every day, and the gallery keeps growing in one place.

If the days are really separate events with different guests, such as a rehearsal dinner and the wedding itself, consider one event per day so each group sees only its own gallery, since everyone with a code sees everything uploaded to that event.