Noone knows the exact words that will be on the exam, but the better your vocabulary, the better your writing, and the more chances you have to recognize and understand difficult words on the paper.
My live streams are 1 to 2 hours long because I only stream once per week. I try to get a significant amount of work done in each stream. If the stream recordings are too long, you can skip sections and only watch the parts that you find useful. Hope this helps.
