Device Properties — Connection
The Connection group configures subscription timeout and keep-alive properties.
Lifetime Count: Specify how many times the publishing interval can expire without the OPC UA Client sending data updates or keep alive messages before the server deletes the subscription. The larger the lifetime count, the longer the subscription remains running if communication is interrupted. The valid range is 3 to 300. The default is 60.
Keep-Alive Count: Specify the number of publishing intervals that must expire before a keep-alive message is sent. The valid range is 1 to 10. The default is 5. 
Note: Smaller Keep-Alive Counts increase the amount of communication during periods when little data is transferred between the OPC UA Client and UA server. Larger Keep-Alive Counts decrease the amount of communication during these periods but also make the driver less responsive when the connection is interrupted.
Note: Smaller Keep-Alive Counts increase the amount of communication during periods when little data is transferred between the OPC UA Client and UA server. Larger Keep-Alive Counts decrease the amount of communication during these periods but also make the driver less responsive when the connection is interrupted. Priority: Select the relative priority of the subscription. When more than one subscription needs to send notifications, the OPC UA Server sends data from the subscription with the highest priority first. Applications that do not require special priority should be set to the lowest priority possible. The default is lowest.