There are two settings we are using to help with the load balancing of agents. First is set the combination to "all" so that on the original collector connection status would be 3 and the new collector would be 1.
Second is to extend the periods over threshold from 1,1 to 8,8 (two minutes) typically the load balancing take less than a minute, but could take a bit longer depending on how loaded the EM-collector is.
In the above case, this would not prevent or catch if there is an ADS and the agent is stopped and not restarted. This is mainly due to two factors, first is the trigger alert notification set to 'Whenever Severity Changes".
With the trigger set to whenever severity changes, the value would need to change and not included in an ADS.
The second, is the agent unmount period. If an agent is within an ADS, goes down and the ADS is longer than the unmount period, after the ADS has expired, there is a good chance that the agent will be unmounted thus the agent connection data would be "no data". There isn't an alert setting to catch a "no data" condition.