Help with a simple layover issue

Hello! My name is Ashley I'm new to using after effects, and Im having an issue laying a picture over a video. I have it set up with the image in front of the video, but when I go to play it the image only stays for about 30 seconds before it disappears. I even changed the duration of the image to match that of the video, but it still disappears after 30 seconds. Help me!