How long to smoke sausage depends on the meat mixture you are using and how you plan to serve the sausage. Both size and smoking method will be factors. Tradition counts, whether you're aiming for Polska kielbasa or Louisiana hot links. Most of all, it should be about what you like.
Then and Now
Smoking sausages began as a method of preserving surplus food, but the practice remains popular even in the era of refrigeration, because smoke enhances the flavor of the sausages.
As your sausage is smoking, cut off pieces, cook them and taste them. That is how you will discover how much time in the smoker delivers the flavor you like.
Hot smoking flavors and cooks the sausage with hot smoke. It takes place between 105 and 140 degrees F, and generally requires from one to three hours, although recipes vary.
Cold smoking takes place at 52 to 72 degrees F, and requires from one to 14 days, usually with some breaks for drying.
In general, don't smoke sausage unless you are using a cure containing sodium nitrate, which kills the organisms that can cause contamination. Botulism can kill.