This could be old news and everybody knows it but I was banging my head against the wall. I was attempting to display a stock quote on my client’s site. I found a feed and if I took the Url, pasted it into a browser, and refreshed it, the data would update every 5 minutes or so. I then took the feed and used it in RSS Viewer Web Part and the update would not match the browser - even after I refreshed the page.
Turns out the issue is the OOTB RSS Viewer Web Part has a built in cache interval of 30 minutes. Duh!
Below are three, non-OOTB, RSS Web Parts available:
Hopefully this saves someone some time.
Thanks to John Ferringer for keeping my sanity.