[[mw:Extension:GlobalUserPage]] says "The $wgGlobalUserpageCacheExpiry controls how long to cache the rendered HTML for; the default is 60 * 60 * 24 * 7 (one week)."
Testing at shoutwiki confirms that the GlobalUserPage is cached, and changes to the GlobalUserPage do not immediately show up at local pages.
This point should be mentioned in the main documentation at [Help:Global user page], to avoid user-confusion.
Version: unspecified
Severity: enhancement