I find the License FAQs to be very good, actually. I cannot give you a definitive answer to your question as the information you gave was not sufficient, hence the “most probably” part.
If your videos all belong to the same series, one license is enough. As all your videos are on the same Youtube channel, this is a strong indicator that they belong to one series.
However, as this is legal stuff, it is hard to give a strict yes or no with the information at hand. I forwarded you to the License FAQs, and especially the part about the single application. You should be able to tell if your use case falls in that scenario or not.
If you are still unsure, the best option is to contact Envato Support and describe them exactly how and where you use the items and they will be able to give you a definite answer that I am unable to give (as I am not Envato staff, unlike KingDog who also gave great information regarding the single application part I was talking about).
Here you can contact support:
With the information at hand, I stay by my words: A single regular license is most probably fine for you.