All the fireworks pictures I took were between 2-8 second exposures, so it was a single shot, with usually 3-8 explosions in each shot. The only problem with doing this is that you need to have the aperature stopped down as far as possible since the fireworks are so bright, and the long exposure makes them brighter.
The smallest aperature I have is f/11 on my camera, so I also had a neutral density filter on the lens to keep it from being too bright. (ND filters just reduce the amount of light coming into the lens evenly across all colors to allow for longer exposures without overexposing when you can't stop down any further)