To provide maximum flexibility for future changes, unless I want the free stopover, I always book my "return" SQ Awards as two one way tickets.
This allows for changes of plans (when you book almost a year out all sorts of things can change or are not known at time of booking), plus one can upgrade more easily and cheaply if availability opens up.
Another crucial befeit is that it allows you to snaffle popular redemptions as soon as they open. If you wait for the return leg to open, then the first departure flight may be booked by that time.
A big benefit too is that if you later decide that you want to fly over/ back from different cities that it is simpler to change.
I also often book in and out of different cities. ie next trip arrive in Paris, but return from Rome. So one way redemptions are easier.
I also will sometimes book the two "one-ways" on different airlines and/or FF programs. For example one trip I flew over via a *A Award on SQ for availalibility reasons, but came back on SQ my preferred airline. (When I was redeeming for 4/5 in J availability was a BIG factor. Much easier these days when it is normally just the two of us).