I have been his custodial parent since he was one year old.
It would be a good idea to complete the process before the child turns 18. That way you are able to continue making important decisions for him after he becomes an adult. There are several different types of conservatorships. You should consult with an attorney in person to review the options. There is some good information available at the CA Courts website: http://www.courts.ca.gov/selfhelp-conservatorship.htm.