I make a quart at a time. Never tried any other size. Takes approximately 3 hours at the middle setting. Works out to roughly a gallon per day if I stay at it.
I do not mix water with my silver in the humidifier. I see no reason for it not to work even if cut with water. I usually keep 10-12 gallons made and sitting in a dark closet. When needed I already have lots to work with and I do have several friends and family members that depend on me for the Colloidal Silver .
After a couple of years use, the humidifier looks dirty on the vents. It is silver accumulation. Does not bother me but the boss most likely will want a new one soon.
I have room I built in my basement that is my office/man cave. I recently got a ultrasonic cool mist humidifier with a narrow outlet stream of vapor. Different than the one I use for the family. I run it in here sometimes and when I walk by I will inhale deeply a few times through my mouth and again a couple of times with each nostril. Works for me.