One annoyance about SQL Reports is that every 12 hours (720 minutes) the reporting services libraries remove themselves from memory — they "Recycle" themselves.
The result is that on any given day, when a user goes to the http://localhost/reports web site, they’re stuck waiting for SSRS to load from scratch — which can take up to 2 minutes.
To make this less annoying you can change the "RecycleTime"
Navigate to the SQL-Appropriate version of this folder:
C:\Program Files\Microsoft SQL Server\MSRS10_50.MSSQLSERVER\Reporting Services\ReportServer
Open this file:
rsreportserver.config
Search for RecycleTime:
Replace the 720 value with something larger like 2880.
2880 will keep the services running for 2 days, so the slow start will only be every couple of days, not every 12 hours.
You could also use other values for longer or shorter "stay in memory” times.
Darren Myher's Blog 