I empty my Temp Internet Files daily. Is that what you are talking about with CACHE?
about browser cache yes.. cookies however don't get emptied usually without the user explicitly selecting to do so. And that cache is different from what the logout/login cache that Dish/Sling servers hold for your account. The SHIFT Refresh, is to try to dump what ever the browser has in memory which is not necessarily written to cache files.
Logging out, but leaving another browser window open, has the potential of leaving trace behind that will be incorrectly seen as your user account still holding valid credentials on the server. Its not supposed to happen, but it does.. which is one of the reasons I say to close all other browser windows (and sometimes that can apply to applications that make use of the browser components, not just the browser itself, though this is becoming more rare).
Then there is the cache that the Dish/Sling servers have for your login ID / Dish / sling user and account info.
imagine if you will the presentation to you of your content ... much like "The Ring" in lord of the rings ... "one ring to rule them all, one ring to find them, and one ring to find them all and in the darkness bind them" ... but in dish's and sling's case .. they are servers..
One server keeps a list of all that was and is about your "User".
One registers Sling/Receiver Finder ID's, ports, update info etc
One server interfaces to Dish (what packages you have)
One server for authentication
One server for media monitoring
One server for aggregation
So when you log in, and go to the My Recordings section.. you may not be seeing the contents as they are right now on your DVR, but the cache of the information as Dish/Sling last saw it. The only known way to force that information to be gone (cleared) is the logout/login and refresh button in the My Recordings section of DishOnline (or DRA's refresh).
That cache was found to be a source of problems in the DRA days... and the same problems exist now, but its hard to pinpoint because everything from the outside is pointed at "dishonline" as the url. Old DRA, after you logged in you were handed to a specific server ... and that server held your account information as *it* had collected and correlated it... and that server would show with dishXX.sling.com in the URL .. the XX would be a number from 1 ~ 16 ... now reaching upto 36.
So in trying to clear cache.. not just on your machine, but at Dish/Sling's side to try to bring it all back together again.. make it all go out and re-identify the bits that make up your user and usability of the Dish/Sling technologies.