You should not block for excessive or significant time inside the OPC event handlers (such as an event handler for EasyDAClient.ItemChanged) or callback methods. Doing so delays further event processing, and in serious cases, can lead to excessive memory usage and eventually loss of events.

OPC Data Client internally queues the events, and therefore any blocking in your code cannot have negative influence on the target OPC server. In the long-term, however, the average processing time for your event handlers or callback methods must be equal to or less than the average rate the OPC events are incoming.