Not only packing light is the priority but backing small is equally important. A mattress is probably the lightest material on your backpack but it takes lots of space. To rescue you from this, there came an air mattress. 

Those mattresses can be inflated by blowing air to sleep and deflate for packing. When you deflate, it becomes compact that can fit easily inside your backpack. Just like everything, it does have its own pros and cons. I am just going to list some of them as I have experienced 

Pros

  • Light and compact to carry
  • Comfortable padding from the cold ground
  • Easy to deflate and inflate

Cons

  • Not sturdy for some people
  • You need clean, even surface to avoid puncturing
  • Single-hole can make it unusable and not easily maintainable
  • Somewhat noisy
  • Expensive to buy

You may have a different opinion and experience. On my trip, I had both mattresses with me, as I can’t rely on the air mattress completely and used to use the air mattress only in case the ground is damp. In other cases, I found my insulated foam mattress, sturdy, reliable and comfortable.