When tabbing out or standing still in either sandbox, or the Explore NYC maps, if the shop is within sight but outside FOV so i could see it if i turned but its not currently on screen, turning back to that shop will cause a large number of the glow effects to appear at once lagging the game. not sure exactly how long it takes to build up, seems to be within only a few seconds but its small at that length so its hard to tell. the longer you take the more appear, it becomes noticeable within only a few minutes of not looking.
have not tested if its effected by distance or other factors such as moving without looking at it, or trying to get it on screen without triggering the effect.
have not tested if its effected by distance or other factors such as moving without looking at it, or trying to get it on screen without triggering the effect.