This is what I've been trying to research based on the posts on this forum.
Lets assume a site had multiple images on it. The owner gets a C&D letter over 1 image (not all of them) and takes down ALL the images in 2007. At this point, I'd imagine the site owner is being extremely cautious and wants to prevent these other questionable images from harming them. So the flagged site is clean from 2007 forward. From what I can gather, Getty has no legal ground to sue over that 1 image mentioned in their letter from 2007. But, where things seem to get fuzzy are the other images and archives. Could Getty come back and start this whole C&D or sue over those "long gone" images? Their only basis are screenshots of the site's older state (where the images where there in 2007)... but in this example, it's now 4 years since the website owner used those images.
Also, I'm not considering the idea of other companies sending letters as this is a possibility. My main focus is the actions taken from the same company and if they are checking websites based on their current state (not the archives).
Once the 3 years is over, they cannot file suit for the images contained in the original letter. However if there are other images that are not properly licensed, you may get another letter in the future. Say fro example from a different stock image company..