For anyone wanting longer smoke....
If wood chunks don't smoke long on your wsm, use fresher, as Tim suggested, or denser wood chunks. Hickory, oak, and pecan will smoke a lot longer than fruit wood. Another way to prolong smoke is not to put the wood on the top of the coals until after putting the meat and dome on. (Also less smoke in the eyes!) Pouring lit coals in the middle with wood around it works great, and if cooking overnight I bury some wood chunks down in the unlit.
For the kettle, I put wood chunks on top of the cooking grate over the hot coals to keep them from burning up when smoke roasting chicken. For low and slow in the kettle, this is the big plus for the fuse method.