Layering a mylar blanket under the air mattress actually does help retain heat—can confirm from a few surprise chilly nights. Yes, it’s a bit crinkly and might make some noise when you shift around, but it does trap that body warmth quite well, much like using emergency space blankets. The trade-off is sometimes you get a bit of condensation (especially on damp ground), so I usually sandwich a thin towel or fleece between the mylar and the mattress to catch any moisture—works pretty well and keeps the mattress dry.
About patch kits, patience truly is the secret ingredient. I’ve also had decent luck improvising with vinyl tape in a pinch, but it’s definitely not a long-term fix, especially if you’re moving the mattress around a lot. The plug area hasn’t caused me too many problems but I always double check it before inflating, just to catch any sneaky leaks early.
Anyone tried storing their mattress partially inflated when not in use, or is it always better totally deflated? I’ve read mixed