I stopped reading many of these, because they're all so similar. A couple things I'd consider when determining what my EF should be:
1. What kind of expenses can I realistically expect based on my lifestyle? That's to say, what do I have for debts outstanding, health conditions, car expenses (do I drive a fancypants Escalade?) etc?
2. What kind of drag on my portfolio am I willing to accept to have access to cash at the drop of a hat?
a. Remember, saying that you might need 10,000 dollars TODAY is pretty unrealistic. You can pay for almost anything with a credit card.
3. Is there a better way to cover emergencies? What about a HELOC? Mine gives me access to 5 figures same day, should I desire it. The interest rate is something like 1.99% for the first 6 months.
4. How secure is my job?
5. How big is my money mustache?
For your dollars that aren't sitting in a real investment vehicle like VTSAX, you're willingly forgoing that magical 7% return (or whatever you have told yourself the stock market can give you every year). So if you sit on a 10k emergency fund for 10 years, you just lost what - 8500 bucks? Give or take? There's your emergency fund right there. And if you're a real mustachian, you can cashflow most emergencies because an emergency to the average American is probably a surprise $500 bill. That's small potatoes to you, right?
All of this 6 month expenses in cash is horseshit, unless you're in a high risk profession or feel you're at risk for losing your job and would have a problem finding another one. Even then, the returns you forego with a large emergency fund likely outweigh what you gain by having cash on hand in case of an emergency.