The average YouTube video gets gets 50% of its views in the first 6 days, according to TubeMogul via Silicon Valley Insider. After 20 days, a YouTube video has had 75% of its total views and the average video lifespan is probably getting shorter. In 2008, it took 14 days for a video to reach 50% of its views and 44 days to hit 75%. Lesson to marketers: post early and often.