I pull heads immediately and ice. Technically you have to save the heads until you return to shore (except for May) because there are actually two limits, 80 spots and 10 pounds overall (there are other shrimp open in some areas).
It's a part of the regs that needs cleaning up, if the area is only open for spot shrimp, or you only retain spot shrimp, there should just be the 80 shrimp limit.