How often should I set Ads on YouTube videos?

Hi everyone. I have got a channel where are uploaded 10-11 minutes long videos. I have on every video ads in these time period: before video, 1:00, 3:00, 6:00, 9:00, after video. My earnings are low. CPM is 1 USD. Is it possible to change ads time period for every video in order to increase my YouTube earnings? What is the best time ads for YouTube video. I don't know what should I change in my YouTube Ads tactic to make more money than 1 USD for 1000 impressions now? Please, help me…

How often should I set Ads on YouTube videos?