Dreamstation Humidifier Water Usage?

I started with the Dreamstation back in March 2020. The humidifier setting was and is still set to '5' which is maximum. When I started out in March a tray of water filled to the max level line would be pretty much gone by the morning, occasionally dry. Now in in August there is about 1/4" to 3/8" of water left in the tray in the morning. Is there a mechanism in the Dreamstation that controls the rate of humidity (varied temperature of the heater) added to the air flow that is dependent on humidity in the room or could my breathing rate while asleep have changed that the air flow is less than when I started, thus the air flow through the tank draws less moisture? I don't wake with a dry mouth, so I assume the humidity is adequate. I'm just wondering why it seems to use less water.

The ambient room humidity will affect water consumption along with excess leaking and the pressures in general.
Most likely reason....your ambient humidity in your bedroom has been a bit higher.
I know when it rains I use very little water when compared to the non rainy nights....even with windows closed.
It's been a bit drier than usual lately and I am using almost all the water each night but last week when it rained all night I used very little water and I didn't change anything in terms of settings.

So yes...there is an ambient humidity sensor built into your machine and when it senses so and so humidity already it will reduce the amount of heat to the humidifier plate which is what ends up controlling the amount of humidity delivered.