When my son crossed over from Cubs to Scouts, I went to Sam's Club and bought a 3 inch self inflating foam matress. It was certainly better than sleeping on the ground like we did in scouts when I was a youth, but I still was somewhat uncomfortable and had trouble getting to sleep (bad back). I upgraded to a 6 inch Coleman air matress and got the best nights sleep camping ever. When we went backpacking at Philmont, I had to go light weight and got a 1.5 in Thermorest (Campmore, they frequently run sales on "seconds"). Slept well, but I think that had more to do with exhaustion than comfort.

I hear a lot of "get rid of your air matress" in these posts. My recommendation is keep the air matress and get a warmer sleeping bag or more insulation between you and the matress. I don't mind sleeping a little on the cool side, as long as I can get to sleep. I have a -5 degree bag that works very well for winter camping. If you are carrying gear long distances, then you need to go light weight and a self inflating foam matress is better. If not, go for comfort. If you are young enough and your back can conform to the ground, go for the thinner foam. If you are like me and wake up after a night on the ground with thin insulation, and feel like Quasimodo, beef up the insulation between you and the air matress until the heat loss to the air matress is tolerable.