Well there is not doubt you get to travel a lot on SQ, but wouldn't it be nice to try some other airlines during your RTW trip?
The great thing about *A RTW tickets is that you can mix and match carriers as much as you want, and there are plenty of other nice *A first class products to try. As far as I can see the only other airlines you're flying other than SQ is LH LHR-FRA (short flight, and in C) and possibly UA JFK-SFO (nothing to write home about, even in F).
I don't know how many SQ segments you need for PPS, but otherwise both LH, LX and NH F are very nice and could fairly easily be included in your itinerary.

Also, as already mentioned, you do have over 2000 miles left, it would be a shame to waste them wouldn't it??