Task Schedule for Windows 7, (may have to tweak since I don't have a Pirelli), attached below.
You'll need wget.exe which is in the archive, I've put it in C:\ for this purpose but just move it wherever and change the Task accordingly.
1) Open the Task Scheduler and import the Reset Pirelli.xml
2) Task is listed, double-click to editrestart router after few minutes of inactivity
Change the parameters as you like.
A bit more info on what constitutes an Idle state wrt the Task Scheduler:
You can set a condition that tells the task to run only if the computer is in an idle state for a specific amount of time when a trigger is activated. When you set this condition, you also set the amount of time to wait (after the task is triggered) for the computer to enter an idle state.
The Task Scheduler service will check if the computer is in an idle state every 15 minutes. A computer is considered to be in an idle state when a screen saver is running. If a screen saver is not running, then the computer is considered to be in an idle state if there is 0% CPU usage and 0% disk input or output for 90% of the past fifteen minutes and if there is no keyboard or mouse input during this period of time. Once the Task Scheduler service detects that the computer is in an idle state, the service only waits for user input to mark the end of the idle state.