It will depend on
a) Collection interval of your player and of course connection to the CMS
b) Duration of your layout - as it will be updated when the layout reloads or when the region with your dataSet/ticker reloads
c) Ticker/DataSet View has it's own update interval which you can adjust.
Does that mean the dataSet is on the default layout or does it means that the layout with dataSet is not displayed at all?