At this point you have 2-3 chars that post your glyphs for you. It became too much work to move them into and out of the bank. A few classes of glyphs are dedicated to each alt. You know by color what glyph goes to what character.
Your operation is huge at this points. You feel like you control the herb prices on the AH. They never drop below your buyout price. Your stockpile of ink would last a week without restocking. You craft your glyphs to a full stack when you craft.
Snowfall is a dead item. You produce so much of it that you will never be able to unload it. You do what you can with it but now consider it worthless for your calculations. This brings your cost per ink up and even with a minor adjustment in your threshold you are sill making a profit on the glyphs.
This is the point where you realize that you spend way too much time working inscription. The gold is great and comes in fast, but the time commitment is killing you. You mill it all yourself because nobody can supply you with all the ink you need. You control the market and you know there is no possibly way that your competition can spend as much time as you on it. You outproduce him and you know he cannot keep up.