You can always make extra Challah dough to freeze and bake at a later date.  There are two ways to do this; both give excellent results.

Method #1:    Wrap leftover dough tightly in three layers of saran wrap. Thaw when needed for at least three hours.  Kneed, allow to rise for two hours.  Shape and bake.
Method #2:     Allow dough to rise, shape into loves, place in freezer until hardened, wrap in saran wrap in three layers, freeze until needed.  When thawing, remove saran wrap, allow to thaw/rise for three hours, then bake.