Smoke is adsorbed. We only use 2-3 "chunks" of wood. It will last 1 1/2 to 2 hr. That's all that's needed. If you find that there wasn't enough to satisfy your taste buds, add ONE more chunk next cook. A chunk is generally around 2"-3" square. The bigger it is, consider using 2 instead of 3.
You definitely do not want to keep adding wood for the full cook. You couldn't eat it.