You may only post original content created by you in the Tips & Tutorials forum. This doesn't mean that you are necessarily the first person to have ever had the same idea. It just means that you aren't plagiarizing someone else. Your tip or tutorial could also be a novel approach for accomplishing a familiar task. In addition to what Emiliano said about "attaching" videos (or images or any other digital content) for which you aren't the copyright owner is a violation of the Digital Millennium Copyright Act of 1998. So, embedding a link to the file on YouTube or Vimeo etc as John Kelsey did is the correct and only way allowed.
Regarding your concern about content disappearing, we have no control over what happens on other websites such as YouTube. However, content created on the AAW forum has been remarkably permanent in the nearly eighteen years since the forum's first post in April 2004. You can bookmark posts so that they will be easier to find later.