I understand. To be honest I don't think this inflight replanning expecting less consumption or more favourable winds, being able to use contingency and so on, is something we have ever planned on to get somewhere. Our planning strikes me as quite accurate if not vaguely optimistic and rarely we end up in the plus side. Sounds interesting though. And the going to the alternate with your final reserve plus whatever is left extra I guess it's a matter of picking the right alternate then. Seemingly, if we had changed the destination alternate, that would be an inflight replanning though.
Anyway, thanks to you all for the responses. It's always a pleasure to learn something or relearn something I must say