Its not related to is connected services. Is connected only shows if the agent is connected to Thhigworx platform or not .
And I believe when you say that EMS agents keep alive each 60 seconds , you mean the data value on thingworx for certain property is updated after every 60 seconds .
Updating of Property value depends on cache time . Please let me know if this is what you are asking about and also if you want detailed description of how cache time works.
there are two components to a websocket disconnect, the configuration in the EMS and on the platform in the WS (WebSocket) Communication Subsystem, see last paragraph in the Thingworx Edge Help pages:
On WS Communication Subsystem it is parameter "Idle Connection Timeout (sec)":