Auto Refresh
A dashboard on a wall shows whatever it loaded this morning until somebody presses F5. This refreshes the data behind it on a timer, and says when it last did.
It says when it last refreshed
The last refresh, a countdown to the next, and a Refresh now button for the reader who cannot wait. A dashboard that refreshes silently is a dashboard nobody knows whether to trust, which is the same problem as one that never refreshes at all.
One refresh per data source, and none while nobody is looking
Four sheets sitting on the same source produce one refresh, not four. And a dashboard in a background tab is left alone until somebody looks at it again, because on a live connection every tick is a query against your database. Thirty seconds is a floor, enforced whatever is typed.
A refusal is shown, not swallowed
A published data source that needs credentials is reported in the words Tableau used words, and the last refresh time does not move. A refresh that did not happen is not counted as one, so a dashboard never claims to be up to date when it is not.
