Update: I finally decided to take the time to run a second 20’ cable and I’m happy to report that neither of those two cameras (v3s) have gone offline since then. This was done on August 2nd so almost 2 months now since I made this modification. 
The two USB cables are plugged into the dual port Anker power adapter I linked to in my last post.
Anyway, I was pleasantly surprised that the time I spent running the 2nd cable proved to be worth the effort and thought it was worth updating my results in case anyone else is having a similar issue.