When I am doing it I usually go over several hours. I start the smoker at 100 then increase every hour by 10 degrees until I get to 170 then I wait for the sausage to rise. Depending on how thick the sausage is it can take 10+ hours.
I have 2 more degrees I put a good thermometer in the top of the MES40 and it was about 12deg off I bumped it to 183 and thigs are looking much better. the sausage casings are I belive 35mm. Will take pics shortly and post.