Extending The Life Of My Skirts By Adding Elastic?

If you haven't grown too much you can loop a rubberband through the button hole and then back through itself and secure the button with the rubberband. Don't know what to do about the zippers, though.

I read a letter from a woman who sews clothing for many of her (long-distance) relatives. She says that instead of finishing the waistbands of these garments, she sews a buttonhole on the inside of the waistband, pulls both ends of the elastic through it, and secures it with a safety pin. This way her relatives simply try the garment on and sew one line of stitching or just re-pin where they need it!