title: Does Cache.Insert with CacheItemRemoveCallback run when no user is on the page?
body: <p>I'm using cache insert to refresh cache on a page every 20 minutes, for example:
  Cache.Insert("x", foo, null, Cache.NoAbsoluteExpiration, TimeSpan.FromMinutes(20) CacheItemUpdateCallback) </p>
  
  <p>I'm wondering if even though there are no current users on the page, the cache will refresh every 20 minutes?</p>