We are glad to hear that you like Telerik Reporting and use it in a DNN web site. Unfortunately, until now Telerik Reporting is an embedded reporting engine which means it is always part and in command of a 3rd party application. The requested functionality tends to be a property of a reporting server like the Microsoft's Reporting Services.
Although, currently we do not offer such functionality out of the box I can imagine several possible solutions.
You can create a separate application (a console application should be good enough) that is responsible for rendering a report in a given format; then use the Windows Scheduler to schedule this application run in a timely manner and generate reports at any time; you can use configuration files or command line arguments to specify which report and in what format to be exported.
Other possible solution is to create your own scheduler - create a timer to check the current time and in case you have a scheduled report - render it.
Here is a KB article
thread that explains how to render a report programmatically.
I hope this information helps. Please let me know if I can be of any further help.
the Telerik team