This is my methodology, as I have learned thus far from many folks and years.
When cooking "Low and Slow"...my general Rule of Thumb is that I want 4-6 hours of thin, blue line smoke. Not thick smoke, just a wisp of it coming out for 4-6 hours.
Once meat becomes surface dry, and reaches a temperature of around 160F - it will no longer adsorb more smoke, so you want to get the smoke profile right at the beginning of your cook. You may extend it a little by spritzing the meat with any moisture source that is appropriate ( beer, apple juice, water, etc...) but be careful not to wash off prior smoke with too much liquid addition to the surface of the meat.
Pre - cold smoking your meat may also allow you to create the flavor profile you desire, without as much problem. Try the Amazen Tube Smoker - prior to lighting the charcoal.....