It depends on what kind of shape the trails are in !....I would say with smooth runnings every bit of 8hrs at a decent not out of control pace,and thats taking in a few breaks and a lunch without alot of thumb juice..did that trip a few years ago with 5 of us and we don't ride that aggressive with the guy's we were with..you should try too stop at some of the outlooks and other stuff too see along this trip-break it up with a stay over along the way,Big Bay would be a nice town for ya too shoot up to and spend the nite,if you have never been there it won't disappoint you,nor will the trails up there..In Marquette behind the AC dealer there was a brand new trail that led you up that way to Big Bay.
VERY important I think in L'anse the trail might be shut down,so if the ice conditions are rite you could jump on the bay from the boat launch to get over to Baraga trail system then from there again with the same good ice conditions you could get the trail thats shut down(4 get the trl #) this is the one that goes to Chassel,if you could take the patience to hit this trail you would save yourself about 3 hours,it puts you on the bay at then its with smooth ice only a 15 minute ride at a wide open pace to Houghton....Im sure there will be more feed back for ya here as everyone has been very clear about other people's need's..Have Fun !