The #1 advantage of internet advertising, is the fact that what you chose to display may be changed at any time. Print ads are permanent fixtures in magazines, and due to the lead time involved, cannot be used for "real time" updates to your products. At GSN you have the ability to run a different ad every hour if you wish. Your ad will be most effective if it's used like a "daily specials" chalkboard at a deli, rather than a "roadside billboard".
Think about it this way; everyone passes billboards on their daily drives through town. You notice and read it the first few times you drive by, but soon it just turns into part of the "background". The chalkboard at the deli however, you look at and read every time you walk in, because there is always current and pertinent information on it. You may not want the hot pastrami sandwich today, but you'll check it tomorrow because they may have something you like.
In relevant terms: A new ad will attract more attention than the same stale ad that's been the same for months. The users also recognize constantly updated ads, and actually start to look for them as they browse the site, to see what's new and hot. They also make an association between sponsors that are constantly updating product lines, new in-stock items and such, with sponsors that are interactive with them and responsive to the ever-changing nature of the hobby business. Imagine the power you hold, when the users are just waiting to see what you're going to have on your ad next!