Visconti

Will be flying, at least quarterly, SIN - TYO; usually, I just take JL direct in J. But, if I opt for CX, which goes through HKG with a layover, may earn enough points for DM. I usually fly J or F, and was wondering if DM is worthwhile what I'm considering? Or, is it just goofy and not worth it? Also, say, if my potential qualifying DM, whatever excess points above the threshold are set to 0 immediately upon the flight's completion?

Thanks.