When it comes to black olives, I strongly-prefer the soft, prune-like,
oil-cured variety to the more-common brined type, which tend to be bland and spongy. The Whole Foods I shop at stocks them in its olive bar. If you can't find them, I'd recommend kalamata olives over brined black olives.
Stored separately, leftover soup and couscous keep well in the fridge for a few days in an airtight container (the parsley will wilt slightly, but not too much). While I don't recommend freezing leftover couscous, once completely cooled, leftover soup
can be portioned out and frozen for up to 6 months.