When connecting to a dashboard for the first time, Tableau normally will be querying the actual data source to render the view.. After that, requests will use cached results, which will generally be quicker.
The cache with then expire after a period of time (depending on what has been configured on the server), which is why the next day the first request again takes longer to run than subsequent ones.
See following post
Hope this helps
From the link you sent, Russell was saying that "Refresh less often" option will cache data up to 12 hours. However from onlinehelp, Configure Data Connections , it will last as long as nothing changes or i misunderstood the statement?
Refresh Less Often—Data is cached and reused whenever it is available regardless of when it was added to the cache. This option minimizes the number of queries sent to the database. Select this option when data is not changing frequently. Refreshing less often may improve performance.
It used to be "forever", bur as I recall things changed when we added the external cache in v9.x. Since then it's been 12 hours. I can double-check to be sure, but I think the docs may be wrong.
It'll be great if you can help to double-check.
Does the cache work by user? If my login is able to see all data and I login to view the dashboard, will subsequent users experience longer response time opening the same dashboard?
Also, may i ask if there is a way to know when the 12 hours start from? Many thanks.