I honestly don't think it makes a difference when and how you check in. I travel with a group of Gold and Plat holders regularly, and we've exchanged notes. I once got upgraded without checking in online and within an hour of check in closing, and my colleagues who'd checked in a day earlier got nothing. And the reverse has happened.

Havent seen any convincing logic to the upgrade system at EK, short of having status improves your chances. Hopefully someone will be able to give a link to where it's been worked out. Relative newbie to the forum myself.