Update Chrome OS Flex live image?

[mr_master]

So I'm currently trying out ChromeOS through ChromeOS Flex to decide if buying a Chromebook is for me. I am not installing it on the machine I'm testing it on, so I am doing it through a USB drive with a live image of it. Am I able to update the live image without losing the current data it holds? The data does persist on the USB after restarts, unlike on most Linux distributions with live images. Or will I have to update it by re-flashing the image through the ChromeOS recovery app?