If a user moves off of a page without waiting for all that Pages components to download, how does that effect the Page timing metrics such as Page End-to-End Time.
Also, what if that Page is defined as a required step in a Service? How does that effect the Service End-to-End time?
FxM will still measure the page times based on the components completing their download. If, for example, a Page has 10 Page Elements/Hits associated with it, and the user leaves the page after only 7 of the 10 have had a chance to complete, then the 3 that didn't get a chance to complete will not be contributing their times to the total for that Page and thus for the total of that Service.
For a service to be considered complete and its metrics incremented, all the Service Steps (Pages) in that Service must be visited. Even if not all of the Page Elements/Hits associated with a particular Page in a Service get a chance to download, the download of just the top-level initial Page is enough for FxM to deem that that service step has been satisfied.
So if say 20% of your users are hitting the "next" button on our splash page after 6 seconds, then the result end-to-end times for that 20% of the users would be 6 seconds