How important is it to treat flare-ups and how do you know when?

I was diagnosed with bronchiectasis in 2016. In November 2022, a bronchoscopy came up with H-influenza and MAC. I was given Doxycycline for the H-influenza which stopped the constant violent coughing, took away the fatigue (which I was blaming on age!) and improved my breathing. The cough had been getting gradually worse over three years or so because my pulmonologist from 2019 on didn't schedule follow-ups, just said, "Call me if you need me," whatever that meant?? Since the CT scan "showed no significant change" from the one done in 2017, and I felt so good after the Doxycycline, I opted to watch and wait instead of going on the Big 3 as the doctor wanted.
Yesterday I saw him for follow-up and, as it happens, the last couple weeks my cough is back and getting worse. I've gone from almost no coughing and lungs feeling really clear to more and more frequent coughing and mucus coming up almost constantly. He was focused on the MAC and not waiting too long to treat, which I was happy to discuss, but I was also concerned about the cough and congestion. (I've been nebulizing 7% saline with Aerobika twice a day, and upped my walking.) He did give me another Rx for Doxycycline, whioch I'm now taking, but I do have questions.
I assume that any infection (flare-up/exacerbation) will potentially add to the bronchiectasis, which would mean it's important to treat. Is that right?
How do you decide when to call your pulmonologist?
Is sputum collecting and culturing important?
What questions should I be asking my doctor in regards to flare-ups?
(I have a low normal temp and didn't go much over 99 even when I had walking pneumonia, so that's not much of a clue in my case, just the coughing and mucus moving.)
My pulmo is giving me a referral to Dr. Kevin Winthrop, Infectious Disease, at Oregon Health and Science University, who studies MAC specifically and who is my doctor's go-to person on these things. Ironically it was a video Dr. Winthrop did last year that convinced me that with my stable CT scan I could wait for treatment. He's 5 1/2 hours away, and I'm sure it will be months before I get an appointment, but I'm looking forward to meeting him or someone on his team.