I started backpacking 60 years ago. If we slept on anything other than the cold ground, we used foam pads because air mattresses were too expensive and too heavy.
When Thermarest came out with the CampRest self inflating pad, I was quick to get one. What an improvement in comfort. It was a heavier than the old foam pad but the difference in comfort was worth it.
Air mattresses have been around for a long time but they were heavy and prone to leaks. Then they came out with lightweight mattresses and I got one of those. They were even more comfortable than the self inflating mattress and they weighed less. But they were cold.
Then they came out with insulated air mattresses. Problem solved, right? I've used a ThermaRest NeoAir for many years. My grandson has a Big Agnes Insulated Air Core mattress and it is also good.
I've always seemed to have problems with inflatable pads developing leaks. So I carry half of a foam pad in an attempt to protect the air mattress from leaks, and as my backup mattresss just in case the air mattress leaks. When an air mattress leaks flat, you have no insulation at all and you might as well be sleeping on the cold ground.
A couple years ago, in May, I had backpacked into timberline at 11,200' and, in the middle of the night, my mattress leaked flat. I filled it up with air again and that lasted fan hour or so. I gave up on refilling it. Fortunately I had the half foam pad. That, plus my backpack kept me warm enough to make it through the night.
I've gone back to using a self inflating mattress. A t least when that leaks you still have some insulation.
I don't think that R value is all that important. Sure some insulation is good but that doesn't mean that more is better.
