A 6 inch round brush in an 8x8 flue? That's not a small miss, that's leaving the entire corner of every single run untouched for months. Creosote builds up in those corners first anyway since the flow is slowest there, so you were basically feeding it a place to hide on repeat visits. How did nobody at the shop catch it before a 30 year guy had to tell you?

So here's what I really want to know: did the bins ever turn into hiding spots? That's why my old system fell apart. People would shove stuff in the bin, close the lid, and call it done, so after a couple weeks the plates were still crusty and nobody wanted to touch them. The pointing thing works great until someone's bin hits the overflow point and then it's a standoff over who blinks first. Did you two ever set a rule about when the bin has to get emptied, or was it just vibes? Because that's the part that killed mine, the boundary was clear but the deadline wasn't. What happens when you're both out of town and the bins just sit there for a week?