How did those IIS application pool recycling options go, again? Here’s a good document

With Microsoft's IIS web server, the application pool recycling options can have a great effect on how your application works and behaves on the server, especially if your application must constantly run certain tasks on behalf of your users.

On IIS.net web site, there's a good document available about all these recycling options. In case you are looking for the reference documentation, this is the place.