Ruhlman and Rytek Kutas both recommend about 180 to 200 degrees. Too hot and you cook it and render the fat rather than smoke it.
The goal with sausage is to get color and flavor for "later". The sausage, according to Ruhlman is best cooked slowly, I think he uses the term saute', in order to preserve the character of good sausage and, yes, to avoid breaking the casing.
So, if you are smoking for later use cook slowly to at 155 cool and rinse the sausage and store in the fridge or freeze it.
If you are "smoking" to eat right then, I'd still go slow up to 165 and chow down.
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