This is a recipe we used at kindy and it lasted the week long with 45 kids using it every day. With my kids it lasts for a few months!!
2 cups plain flour
1 cup salt
4 tablespoons cream of tartar
2 tablespoons cooking oil
2 cups boiling water
Place all dry ingredients into mixing bowl, add the water and food colouring and mix with wooden spoon until all combined.
Turn out onto floured bench and knead dough until nice and smooth (be careful it will be a little hot).
Store in air tight container or zip lock bag.