3-4 posts throughout the week should be enough for an EX, so long as you post at the beginning, middle and end of the week. I know some people have gotten an EX by posting a couple of times in the last two days but I wouldn't take the risk, since the criteria says that for an EX, 3-4 posts need to be made at regular stages throughout the week.
Just remember to ask questions and engage with the other students. Just make it look like you're trying to make an effort.
Don't worry about posting too much, they're fine with you posting 10+ times
does anyone know how to increase the speed of echo360 lectures that have slide capture?
I download the lectures and use VLC player which can speed them up