I think to initially gain more views your videos should be 2-4 minutes in length. New viewers are judging you to see if they like you at first, and viewers do see the time of a video. If they don't know who you are and see your video is longer than 10 minutes, they are less likely to click on your video. However, if you have an audience you could try to slowly increase the time on your videos. Every video you make you could increase by about 30 seconds. Your videos will soon be the length you want them, and your audience would not of felt the change so drastically and with more views on your video, newer viewers will be more likely to check out what your about.