My wife did the Arrowhead 135. Bailed at the half way point her first year when the temps hit 45 below F. Finished the second attempt in 2012 on foot.
There are other, shorter, winter snow events. The Triple D (Dubuque, Dysersville, Durango) is about 45 miles and is 500 miles farther south than International Falls. Fat bikes are the norm as much of the route is off road.