I’ve never know for sure. I usually stop when I’m either too exhausted to go on or when I do i feel like nothing more is making a gurgling or wheezing noise when I huff and I know there’s nothing else that will come up.

It's impossible to clear "all the mucus" since we need mucus in our lungs to live. With bronchiectasis we aim to expel the "extra" built up, accumulated mucus (called phlegm, when expelled it's called sputum). Removing the extra, trapped phlegm helps us to breathe more easily, rid bacteria and prevent infection. Phlegm gets trapped in dilated, floppy portions of our lung tubes wherever the bronchiectasis is. For me, the first several huffs of the day are thicker, have more color but after 20-30 minutes of airway clearance the sputum appears less in volume and a lighter color. Your mileage may vary! This is why bronchiectasis is considered a heterogeneous (diverse) disease.