Answer
The Notification Server gives out 10 codebases at a time. From this value of 10, the agent then randomly selects 6 of these codebases to speed test. The resulting server selected then remains the primary codebase for 6 hours, at which time, speed is eligible to be retested for other package requests.
There are settings to control these values. To control the 10 codebases setting, the following should be added to the coresettings.config file on the Notification Server. This entry is not included in the file by default.
<customSetting key="MaximumCodebasesPerPackageServerPackage" type="local" value="10" />
Each individual agent can control the wait time between speed tests. This is a registry value on each individual agent computer. Note that reducing this value will increase network traffic. The registry key is found in:
HKLM\SOFTWARE\Altiris\Communications\Speed Expiry (mins) (default 360)