Are you planning on flying in Y, C or F?
A couple of ideas:
fly to Europe on LH or UA; SFO-BRU/MXP on UA shows a weekly e-fare of $299.
fly to South America on UA; check out their weekly e-fares
either of these will get you 12,000 flight miles, which with the 1.25 SEN uplift gets you 15,000 miles.