Anytime. There are alternates, like placing other non-Elite in B between A and C, and you in D. That way, if nobody is upgraded, you're all in a row.

Or placing yourself in the middle seat, so if you are upgraded, A, C and D are comfortable and closer together (though I don't like this approach - bad outcome for you if not upgraded).

All depends on what you and your friends like to do on planes.