Are you supposed to keep an air mattress plugged in all the time?
No, you should not leave your air mattress plugged in all the time.
TLDR; The air mattresses with built-in motors can remain plugged in all the time but it’s not advised. Simple power spikes or random natural events such as a lightning strike can burn out your motor. For maximum safety you should unplug your air mattress motor after use.
All air mattresses (low cost and also high quality) will naturally deflate overnight. Although they are designed to hold air they are not airtight. Depending on room temperatures and simply laying on the air mattress can cause this natural air deflation.
It’s better to leave the mattress inflated versus deflating daily
If you’re going to use an air mattress multiple days in a row, it’s better to leave the mattress inflated.
When you continuously deflate and re-inflate an air mattress, it places additional tensions on the edge seams.