It will exist on the page as long as the page exists. That is, it is not a “rented” link or a link that faces temporary restrictions, like a listing as a speaker on the frontpage of a major conference website, or as a sponsor of an upcoming, yearly event.
Its positioning/stance in the current site architecture makes it unlikely it will ever “fall off” the link graph. Many websites, namely blogs, have a temporal state that poorly aligns with site architecture, meaning that your link will eventually be more than 10 clicks from the homepage. When this happens, and no other external links have been obtained, it is a near certainty that it will eventually be worth but a sliver of value, or completely fall off the link graph.
It exists on a domain with an upward backlink growth trend. If a webmaster is still actively promoting his or her website, it is a near certainty that link growth continues to trend upward. On the opposite side, if a website is trending downward, it is probable that the webmaster cares less, the topic isn’t as important, and overall, future link value will decline.
It is not off topic on the domain in question. Manipulative, off-topic links trigger disdain in the users that observe them. Even if historical trends show an upward climb, if your link is off topic and prominent, now, that’s a good sign that the future value of the link will trend downward.