Hi Shaon,
My links are expiring, and i believe it is by design from dropbox. From the drop box site https://www.dropbox.com/developers/dropins/chooser/js
Link types
The Chooser can be configured to return one of two link types.
preview links are the default type of link returned by the Chooser. Preview links point to a human-friendly preview page of a file and are great for sharing. You can read more about links to Dropbox files in our Help Center. Note that users may disable this link at a later point if they choose.
direct links point directly to the contents of the file and are useful for downloading the file itself. Unlike preview links, however, they will expire after four hours, so make sure to download the contents of the file immediately after the file is chosen. Direct links also support CORS, which allows you to read the file information directly in the browser using client-side JavaScript. These URLs should not be used to display content directly in the browser.
I changed your code to instead use preview and modified the URL dropbox is returning to use dl=1 instead of dl=0 and my download links no longer expire from dropbox.
Could we have the option to use either preview or direct in the next release perhaps? This may be new functionality from dropbox.
