I have Silver status at the moment (qualified in January 2011).

I have reached 680 points, therefore I have done enough to retain Silver for next year.

I am considering a trip in December which will earn 360 tier points, however, I am worried I will lose these as they will effectively be "excess" points when my points reset in January (at the end of my year).

Or do the points reset as soon as you get past 600 (not showing this way in my exec club account).

The Sticky thread covers the situation when you first reach Silver, but I can't find any reference to the renewal situation.