I do toppers out of fondant all the time.
I usually let them air dry for a few hours or overnight, so they are firm enough to handle without breaking and and can stand up in an icing swirl but still soft when you bite into them. Then I'll put them in an airtight container until I'm ready to use them. I use little individual candy ziplocs but you could put them on wax paper and put them in a bigger ziplock too. They'll last a really long time as long as you keep them sealed and away from any light source so the colors don't fade.