I havent had any issues in slower traffic with my most recent Clickbank product review video, I posted one back in August and I've gotten consistent sales from it every single week.
Though when it comes to a particular video I posted two years ago, June of 2015 rather, it has seen a decrease I believe simply because I haven't encouraged much activity as far as social signals are concerned. A tool that helps is called Vid IQ, go down their SEO checklist.