We have used air mattress alot when Tent camping...
Used a couple of these twin bed size tent beds with slide in air mattress in the tents... Very comfortable being off the ground...

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We had same problem with the air pressure changing over night and we was always laying in big depression in the mornings haha...
Probably due from outside air pressure always changing when it got cooler and perhaps it didn't hold pressure all that great. Noticed some other pressured up things doing the same thing so I think normal changing air pressure as the night got cooler was some of the problem...
Changed to a foam mattress and found out it likes to get real hard when it freezes up at night haha... Pillows hard as a rock with the outline of your head in them hehe...
Roy Ken