More than that.
- Keep them on separate servers, preferably even separate hosts
- Keep all emails, whois information independent of one another
- Don't link to and from adult to mainstream
Consider it a separate entity. Business 1 and Business 2.
With reverse IP tools and companies storing data online to match your mainstream information to your adult information, one could harm the other if you plan on seeking investment or sale in the future.
Just my opinion, not because you should be ashamed of adult
