We are experiencing a slow start up time on the first report request of the day, or when there have been no report requests for an unknown period of time. In SQL Reporting
I did not find the parameter referenced in tcc'sresponse. However his response did clue me in to the existence of configuration file; I did find a page that had detail on the contents:
MSDN: How to: Modify a Reporting Services Configuration File
In it I found the RecycleTime parameter. It defaults to 720 which feels like the 20 minutes or so it took to time out. I set it to 28800.
I restarted the Reporting Services service for good measure, and accessed the site. It took the usual minute or two to come up and during that time the server was working hard. It is snappy now; I will test throughout the day to see if this keeps Report Services from recycling the process and rebuilding every 20 minutes and report back to this site.