I bet it would last longer than actually lighting the wood chips, at least.

From what I remember, the coal fire lasts about a long as normal...but yes, the chips do burn on they own over time, but not enough to really produce much "useful" heat.

From what I understand, the charcoal fire underneath just helps to creat more smoke. I sometimes will put my wet wood in aluminum foil then place on charcoal, this makes lots and lots of smoke.

In my opinion, I would never burn green wood for cooking, much for the same reason green wood is not used in fireplaces. Green wood will give off a very bitter taste and the creosote build up inside of a smoker will eventually alter the taste of your food. Wood should be well seasoned. I myself have had the most success using lump charcoal supplemented with different hardwoods.

Use the biggest size chunks of wood that you can find It will give you longer burn times. Wood chips are fine for delicate meats and fish because they burn off fast you won't overpower your meat with too much smoke.

All great points you make here Rick!