Was the bar blinking when you pressed it? The bar blinks when it's done and Chloe will also let you know about it.
Yeah. There are ways to shorten the timer! You gotta progress through the story events and you'll be able to unlock Chloe's shop which allows you to buy items for the H-scenes. You can also eat better food during dinnertime to increase your nutrition and higher nutrition decreases H-scenes' total duration (except for the penalty scene)