These smokers use very little wood and you are correct that loading in the beginning will only produce smoke for a couple of hours. Obviously the larger the chunk, the longer it will produce smoke. Lots of chunks produce lots of smoke which can be bad/bitter if it happens all at once. 3 to 6 ounces of wood at the beginning is plenty; adjust for taste. As for using the amps or the like, you may or may not have enough air flow to keep it burning. Resting the drip tray on the ground may help with airflow. From many sites to include Amazing Ribs, the consensus is that meat will absorb smoke only until the meat hits a temp of 140 degrees, and from thereon the smoke just layers up on the surface. There are those who disagree. I can get 3 to 4 hours of smoke, depending upon the weather conditions such as calm or very windy, moisture content of the wood, density of the wood (heartwood is denser that that near the outside), etc.
