Yes, the prewarming cycle just preheats the water in the reservoir. It takes about 15 minutes and then it keeps it on hold warmed up for another 15-30 minutes. It gives you full humidity air right away when you are going to sleep which is more comfortable. There is essentially no humidity added from unheated water. When we camp in our RV with no external AC power and run off the batteries, I turn the humidifier off to reduce the drain on the trailer batteries. Also turn the heated hose off. I do keep the reservoir full of water thinking it will provide some humidity. But, essentially the water usage is negligible over a whole night. The humidifier seems to be totally dependent on the heating effect under the reservoir.
I have had lots of issues with getting a good setup on my machine, and seem to be finally "there" now. In the process I got in the habit of checking the data daily. I also maintain my wife's machine which is an older S9 ResMed. It is true that the A10 can hold lots of data on the card - probably months. The S9 has less capacity for detailed data even if you use a larger card. I think it may be a week, or at the most two weeks of detailed data. And, after that the detailed data is lost. This screenshot gives you some idea what my journey to my current settings looks like. It does not include all setting as some of my earliest data somehow got lost in a "hickup" with SleepyHead.
