A scheduled discovery task was not started

Event ID 10000: A scheduled discovery task was not started because the previous task for that discovery was still executing. 

Discovery name: Microsoft.SystemCenter2012.ConfigurationManager.ClientDiscovery.

I get these warnings on all managed servers for the same discovery type. They come every 1.5 to 4 hours on each system, which makes a mess of the event logs. The default appears to be 14400 seconds, which I have not modified.

Has this been problematic for anyone? Is there a recommended setting if this threshold is too low, or does the fact that discovery is not completing in 4 hours indicate a bigger problem?

Thanks.