The answer is very simple.
Unless you have the most spectacular, unique, useful, versatile and best looking item ever greated at the most ridicolously cheap price, prepare to lose practically all your sales once your item drops from the front page.
Then you will have a couple sales here and then when people stumble across your file by browsing through the categories manually or doing a search (very unlikely). It won’t be worth to mention it. Just consider all old files dead and redundant.
Uploading new files is a good idea, but only the new file will get all the attention during it’s time on the front page. You might get lucky and someone checks out the other files you have created. Out of those, perhaps one or two people might even buy another item of yours as well.
It is also very hard to generate addtional marketing and promote your product off and online. For example if you promote your item on other websites with links to the FlashDen sales page, most people will be turned off by the fact that they have to sign-up to FlashDen before they can purchase the item. They will just turn away.
Unfortunetely there isn’t a way for people to purchase the item directly without having to go through this painstaking process.