Hi Mike
Best to have a small fan to circulate the smoke evenly. The air flow also drops smoking time because it helps more smoke to come in contact with the food making it deeper in colour and stronger in flavour in a shorter time.
3-4 hr smoke with natural venting or 2 hrs with convection smoking. This will give a great colour and flavour
What do you use for smoke? Do you use wood, sawdust or pellets? I always get good smoke flavour but if I get good colour too it usually tastes over smoked. It would be good to know how you get both.
Cheers Wade