The second time I have heard this lately:
Is SQL Server Losing Mindshare.
One of my favorite subjects of late. Just watch out if your variable expression makes calls to a custom assembly. It doesn’t always seem to work! SQL Server Reporting Services Report and Group Variable References.
The trick is to stop and start the RS service at the time of day when it should start up. The recycle time is relative to that, not the time that it last recycled… Prevent SQL Server Reporting Services Slow Startup.