Really depends on what the settings are on both your core and agent.
- On the core server you'll need to check and see how often it's downloading updates, you cal typically find this under the Scheduled Tasks and depending on how or who set it up. There should be a scheduled task to download AV and LD updates, again you'll need to check this to see how often it's running.
- You'll also need to check your AV settings under the Security and Patch Manager config, you should have a LANDesk Antivirus configuration and in there you can find out how often the agent is checking for updates (Virus Definition Updates).
Of course you need to look at the two and then balance them out with your requirements as well, another words it's no good having the agent looking for AV updates every 4 hours when the core is only downloading every 24.
Hope this helps.