The HeartBeatAction is currently called every 30 seconds, and this is hardcoded:

public class DefaultHeartbeatManager implements HeartbeatManager
{
    public static final long TIMEOUT_MS = 30000;

30 seconds can be a bit too quick, and there is no way to adjust this interval (common misconception that this can be corrected with the Draft Save Interval). We need this to be adjustable, to avoid hitting into performance issues with users that left their browsers open in page edit.