2 x R regularly released on some routes - not so regularly on others. Rdpt availability determined by yield management team which varies across routes and various over time - no set formula.
I too have been lucky enough to secure 2 x R Rdpts most routes I want to fly - MEL-Europe / MEL-USA - but best to book as early as poss for certainty or else have a hot line to KF call ctr
I have 2 x Savers F MEL-SIN then R SIN-CDG with s/o in SIN for 2 days next June. Just booked 2 x R ZRH-SIN then F SIN-MEL to ret next July - have also waitlisted CDG dep also for same date - will go back to planning and check which is best for us.
SQ do release odd Rdpt seats if comm tix not sold - again no set formula - KF call ctr staff have no idea how Rdpt formulas calculated or if or when extra Rdpt availability will appear - what they see on screen is what you can book - does that help?