I am curious, did he say why you couldn't use is more?
Sometimes I fail, sorry to say, to ask why they said what they said...."such as: "What type of harm or what are we trying to avoid by not doing it more than one time a day.?"
Wish we were always On Our Toes so to speak with the professionals to have the right question ready to inquire with them each time they say something and don't give an explanation.....it's like a parent telling a child not to do something without being kind enough to explain why they shouldn't do what they are doing." My take on it.
Barbara

My pulmonologist considers it to be a serious irritant, and suggests only using as much asmis needed.
Sometimes I wonder if the constant irritation might be the cause of excessive mucus production by some of us.

As I recall, human testing of 7% saline was 3 to 4 ml once or twice a day - sorry I don't have the study bookmarked anymore. I can tell you from personal experience that the saline I inhale one day is still detectable in my mucus the next - I can taste it.

Sometimes more isn't necessarily better. Maybe if you need an extra boost of fluid in your lungs you can use normal (.9% ) saline - same salinity as your bodily fluids.

Here is a look at several studies, the results are all over the place, but consistently called for treatment once or twice a day. That is also the recommended dose by NJH.

In addition to improving viscosity of mucus, the salinity inhibits the ability of NTM to multiply.

Dr. McShane suggests two 4ml vials to “wet down” the lungs in her most recent AC video. Though she also suggests once a day AC is fine, plus daily cardio exercise. I started doing two 4 ml vials maybe a month or so ago and I find it helps me to be more productive (as someone who is otherwise not productive). I do this once a day. I generally feel well and tolerate the saline fine. I can imagine others whose lungs are more sensitive may not benefit from doubling up, but for me, so far, it seems to be an improvement. Also, if one has a lot of mucus doubling up may not be necessary, and am/pm saline sessions may be more beneficial to help with breathing and cough. But it is a question on my list for my upcoming NJH visit.