I always wonder if I have a domain which is super long, like 20 characters and 5 words... does it hurt SEO
As far as I can tell, no. However you will find that a lot of people (myself included) are hesitant to link to long-domains-like-this.com simply because especially long domain names are normally written off as spammy sites by a lot of webmasters. Obviously less backlinks aren't so good.
No, I have two 5 word domain names and rank in the top 10 for a lot of my keywords in Google, Yahoo and MSN