I received my "fully" approved COE within 24 hours of submitting the required documents and it was more than 48 hours prior to the flight. I submitted the required documents on Monday afternoon and received the approved COE on Tuesday afternoon. My flight is Saturday afternoon.
However, my understanding is that if you have an approved COE prior to 1 November, it will be honored. If it not approved prior to the 1st, you need to apply through the Thailand Pass website.