All very true. My environment is pretty predictable. Typically I order 20 lbs of my favorite green beans at a time, once in a while it's 15 lbs plus 5 lbs of some new type I'm curious about. I'm roasting once in a week to pretty much the same roast level. I hope to be able to figure out how much of the grounds is retained and if the amount changes while the level of beans in the hopper decreases throughout the day. I hope it won't in which case purging will be the same every time I grind. Otherwise, I might need to resort to weighing the beans.

Regarding the extra cost of wasted beans: it does help if you roast yourself. Even high quality beans are rather inexpensive especially if you order in bulk (they never stale).

I ordered Atom 75 a couple hours ago and it should be delivered on Thursday. Looking forward to it and am very curious if it improves the quality of my espresso. I don't count on some drastic change but even a small bit will be great.

Thanks again for your help.

I think you will be very happy with the Atom 75. I also use pretty dark-roasted beans (lately Saka Crema Bar and some home-roasted) with a Pro 800.

At one point I had an Atom 75 and a Specialita paired with my Robot. The Atom is much nicer to use with it's adjustment knob, speed, and LED, but I was hard-pressed to notice a taste difference. I eventually sold both because I enjoyed single-dosing more with the Robot.

Now I have a Niche, and ~4 months ago got an Atom 65, because the Pro 800 can crank out shots pretty fast, and it's much easier to do so with the Atom. I actually chose the Atom 65 over the Specialita for one main reason, the adjustment knob.

I usually don't do a purge, even first thing in the morning. Sure, the first shot might pull in 35 sec instead of 40 sec, but the shots are still more than satisfactory.

"The Wired Gourmet" has a Youtube video where he shims the burrs of a Specialita for better alignment. I recommend taking a look at that, it will be a very similar procedure on the Atom.