I understood the script only checks the front page. Could the change have happened when the article was not on the front page? Or are all articles that have eve

I understood the script only checks the front page. Could the change have happened when the article was not on the front page? Or are all articles that have ever been on the front page supposed to be checked "forever"? I have no idea how often / how quickly an article could oscillate between rank 30 and 31 for example.