Keep gunning in background

When i leave the app by pressing home button and then put my iPod in standby for going to sleep, my battery is always empty in the morning. I always have to remove it from THE multitasking list ( double press home) for saving my battery.

When i have a popularity of 50, leave THE app and dubble press home button and remove THE appicon in THE list of apps , THE popularity goes from 50 -> 10 ( when you have "closed" your restaurant)
So it runs in THE background, it's irritating