Power bank is a much better option than buying multiple Vision Pro batteries. The intention is that the AVP acts exactly like a MacBook, iPad, or iPhone except the battery and USB C charging port happens to live at the end of a cable instead of inside the device. I don't think Apple's intention is for you to fully shut the device down and unhook the battery very often. Supplement it with a 30w USB C PD power bank instead.
I did a bit of calculating based on the 353g official weight of the battery pack and it's likely to be a 20,000mah pack consuming about 10,000mah per hour. I plan on picking up a couple 20,000mah 30w USB C PD power banks ($30-50 each) and running those to extend away from AC power time.