Longest time alone for me, no human contact, was 21 days in the Maine wilderness, July, 1998. To be fair, however, I carried in all sorts of supplies. I did not have to "live off the land" in the full sense. I did fish, eat dandelion leaves, chop wood, sleep in a tent. Despite the season, there were several nights of near freezing temperatures.
(I discovered a way to heat the tent, but I would not recommend it for restless sleepers or those with children. Cover the tent with a plastic tarp except for two vents, one down low, one up top. Place a kerosene lamp on the floor in a secure spot. Be very careful not to knock it over or allow anything flammable to come in contact with it. Be certain the vents are working!)
The scariest part was the visit to my site of a bear. Fortunately, he was just passing through. I also had a cow moose walk right in front of my tent, early one morning. I saw a bull, but not up close. I enjoyed the solitude, but of course, if I hadn't, civilisation was an hour away! The worst part was the biting insects--mosquitoes and deer flies! I emerged looking as if I were suffering from a rashy disease!