I usually stay in a tent for 2+ weeks straight every time GM has their 4th of July shutdown. 18 nights from the Friday I leave home until I pack up on a Tuesday morning is typical. One year there was another week to go with those 2, but I came home to do laundry and mow my grass in the middle of the 3+ weeks, then went back again the next day. The plant my friend works at is shutting down for the whole month of July and I plan on spending as much of it camped at his property as possible. When you spend that many nights in a tent, a comfortable bed is very important.
Several years ago I gave up on cots and switched to an air mattress. My cot is 24" wide between the sides of the frame, barely long enough to lay down on, and has a foam mattress 1.5" thick. Actually 2 foam mattress now, because I took one off my other cot. I have one doorway in my house that's 26" wide from jamb to jamb, and there's only 24" between the edge of the open door and the jamb, the same width as my cot. I can only walk straight through if I pull my arms in, and even then my shoulders still just barely scrape by. No wonder my cot feels too small. I'm actually wider than it is.
My air mattress on the other hand is 39" wide, 75" long and 10" thick. I can't sleep on my back or my face, and when I'm on that narrow cot there's not enough room to pull my knees up and sleep on my side comfortably. Rolling over from one side to the other several times a night is also difficult. My air mattress with its 15" extra inches of width is easy to roll over on, and I have much less pain when I wake up. And if you think I should just buy a wider cot, I've slept on them before and they never felt good. They don't give like an air mattress does and cause me pain anywhere there's a lot of pressure, like my hips. Putting an air mattress on a cot doesn't work well for me either. Another benefit of an air mattress is that it won't rub holes in the tent floor like the feet of a cot can.