overrun past 5 minutes, A casting director only wants to see snippets of your acting, there looking for what you sound like, look like on camera and acting skills. I always try to aim for 2.30 minutes for a showreel, this gets me three clips from three separate films, its straight to the point, no fancy editing just fade in and out. End your showreel with a simple headshot and contact details. if you follow that a casting director will be happy and if your not suitable for the role, they will remember you.