Yes, SS parts tend to be more robust. But while you're figuring out which gear combo you like and whether SS is going to work for you, there's nothing wrong with using your multi-speed cogs and chainrings. I mean, people put thousands of miles on their geared bikes with all of their chainline contortions, so it's not like the drivetrain parts are going to dissolve underneath you by riding them singlespeed for awhile.