As a general statement about sleeping pads and the often heard complaint that they “leaked” overnight.
The laws of physical reality are unavoidable: Air contracts when it cools. So, if you blow up your pad with your breath (warm air, and humid), if you place your pad on the snow and/or if it gets cold later into the night, the air in the pad will contract as it cools. It might seem like the pad lost some air, but it didn’t, and it is not the fault of the pad. Of course, there ARE cases of actual leaks, but I have this suspicion that a large number of “leak” complaints are just the laws of physics in action.
Here’s what my wife and I have learned to do, especially when camping on the snow, but it also works on any cool/cold night:
Inflate our pads a couple of hours before we turn in for the night. That gives the air in the pads a chance to cool down and contract. Then, just before bed we add in a little extra air.
We find that if we do this our pads don’t noticeably sag by morning.
And, we never use our breath, we use a pump sack (Exped Schnozzle). Putting warm air (your breath) into a pad almost guarantees your pad will sag overnight if the weather is cool/cold. And, of course, putting moisture into a pad is good to avoid.