Originally Posted by East_and_West

Not exactly, at least the way I understand your question. Once you qualify for A3*S, both your tier miles and your A3 flights count start over from scratch. So if you need, say, 400 miles for upgrade to S, and fly a segment that earns 1000 tier miles, you are upgraded to S, and your tier miles reset to zero (you don't start with 600 tier miles, so you need an additional 24K - not 23.4K miles- + 4 A3 segments for G). Similarly, if you have flown A3 six times that before you earn S, as an A3*S you will still need at least four A3 segment to be eligible for the low (24K) threshold to earn G.

You don't need to wait a year though once you earn S, in theory you can start collecting tier miles towards G already from your next *A segment (although for practical purposes it may take a couple of days until you are officially upgraded to S).