I can verify that it is helpful to have wipers in place. After 4 days, I notice a shot with 2 grams (!) retention. This evening, I checked the housing and found quite a lot of retained coffee. No wonder my extractions were a bit less predictable this week. New blade stickies going on now.
Is there a forum where this thing is discussed under commercial use? I think it's great, but I wonder if there are cafes sold on it like I am for my purpose.