The line is the single most complained-about thing on the North Shore and it is entirely avoidable.
Peak hours are roughly eleven to three. That is when the circle-island coaches and the Waikīkī day-trippers arrive at Haleʻiwa, and it is also when the Store Lots car park is full and people are circling.
Go before eleven. The queue is minutes rather than tens of minutes, the car park has spaces, and the town is pleasant.
Or go after four. Second-best window, though check closing time — the shop does not run late, and nothing in Haleʻiwa does.
Winter weekends are worse than summer weekdays, which is counterintuitive until you remember why people come here in winter. When there is a contest running at Pipeline or Sunset, the whole coast funnels through Haleʻiwa and the queue lengthens accordingly.
Parking is the real constraint. The Store Lots lot is small and there is time-limited street parking along Kamehameha Highway. Do not park in a neighbouring business's lot; it is towed, enthusiastically.
The genuine alternative: Aoki's Shave Ice, a short walk along Kamehameha Highway, is another long-running family operation making the same product from the same tradition, usually with a queue a fraction of the length. If the Matsumoto line is round the building, walk up the road. You are not settling for something worse.