@bayarea58 Here is the exact quote @pacathy referenced:
"Natural Course of Disease and Decision on Treatment Initiation
Diagnosis of MAC-PD does not require immediate initiation of treatment2,3, and understanding the potential for progression is very important. A significant proportion of patients with MAC-PD (approximately 40%–60%) remain without disease progression for several years after diagnosis, even without treatment12,13,15,25,26. Moreover, approximately 40%–50% of patients with untreated MAC-PD achieve spontaneous negative culture conversion without antibiotic treatment26,27,28. Therefore, to avoid unnecessary treatments that might cause unwarranted medical expenses and adverse drug reactions, clinicians should consider the risk of disease progression and make timely decisions in the treatment initiation phase (Figure 1)."

Here is another article referencing a 30% - 40% spontaneous conversion rate:
https://journal.chestnet.org/article/S0012-3692(21)04293-8/abstract
There are indeed other articles showing the lower conversion rates. Most of the studies we find are small, in isolated populations, so it is hard to draw conclusions.

What is certain is that even National Jewish Health (NJH) and NTM.org support the concept of "watchful waiting" for increasing numbers of people as more is learned about the infection. There is also, as you say, a big difference between those with cavitary disease and those who don't have it. So the decision whether to treat and the long-term outcomes are not the same.

So, for @cholash, and other with low colony counts and few symptoms, not treating WITH ANTIBIOTICS can be a reasonable option. BUT that is not the same as no treatment at all. Daily airway clearance, possibly with saline, carefully managing underlying conditions like Asthma or COPD, getting adequate exercise and rest, maintaining a healthy weight, and taking other precautions are all needed to stay as healthy as possible for as long as possible.