To ensure fairness in the distribution of equity and index option assignments, OCC utilizes a random procedure to assign exercise notices to the accounts maintained with OCC by each Clearing Member. The assigned firm must then use an exchange approved method (usually a random process or the "first-in, first-out" method) to allocate those notices to accounts which are short the options. http://www.optionseducation.org/tools/faq/options_assignment.html
OK I can see that between a "random process" and a "first-in, first-out" process, that it is tailored to screw retail accounts and protect the Club Members. That notice really isn't for my account, right? More to the point and to have experienced ETer's chime in, this butterfly strategy can get assigned even if trading and holding 12 hours 4 hours, etc? I just don't see Augen covering this in the video while trading 10 lots in $300 and $500 priced stocks. Maybe I'm missing something.
I don't know how often early exercise happens, but I have the impression it is fairly rare. Exercising options early entails giving up all time premium, and most people don't take affirmative action that costs them money. That said, I am told that there are occasionas when it is mathematically advantageous to exercise early. I was recently short an option that expired out of the money, but that dipped into the money by a small but nontrivial amount ($100+ per contract) during the period that contrary instructions are allowed. Somebody left some money on the table. I would have exercised the option had I been long, but then I'm a cheap bastard.
I'm not exactly sure what you are asking, but assignment won't happen during the day. It will happen after the close and you will find out about it the next morning. If you close out eod, you won't have to worry about assignment.