Email marketers know that the subject line is perhaps the number one most critical component to any successful email campaign. The subject determines if the consumer is going to open and engage with your email content or not.
The above chart, published by eMarketer based on MailerMailer research data, is far from conclusive. The correlation between subject line length and CTR or Open Rate is not consistent enough to be conclusive. That said, length most likely does play a role in your results. Run tests over time to determine how long of a subject line works best for your various contact lists.