You can bake half of the Spanakopita and freeze the other half. To do this, after step 3, freeze the triangles on the baking sheet for one hour until solid, then place triangles in a resealable plastic bag. When you're ready to cook them, continue with step 4. No need to defrost before baking.
If you have extra phyllo dough, you can make a few with brown sugar and cinnamon inside for yummy sweet treat.