Hi,
For 80 clients I would suggest to change the heartbeat interval to "Push mode" and randomzation windows to 5 mins. It all the clients are in the same LAN then there shouldn't be any concern.
Why did you change default settings?
You can enable or disable the randomization function. The default setting is enabled. You can also configure a randomization window. The management server uses the randomization window to stagger the timing of the content downloads. Typically, you should not need to change the default randomization settings.
In some cases, however, you might want to increase the randomization window value. For example, you might run the Symantec Endpoint Protection client on multiple virtual machines on the same physical computer that runs the management server. The higher randomization value improves the performance of the server but delays content updates to the virtual machines.
You also might want to increase the randomization window when you have many physical client computers that connect to a single server that runs the management server. In general, the higher the client-to-server ratio, the higher you might want to set the randomization window. The higher randomization value decreases the peak load on the server but delays content updates to the client computers.
In a scenario where you have very few clients and want rapid content delivery, you can set the randomization window to a lower value. The lower randomization value increases the peak load on the server but provides faster content delivery to the clients.
Reference: http://www.symantec.com/docs/HOWTO55173