The secret to really long forms is clumping each subject at multiple levels using a visual hierarchy that allows a user to do a quick scan of each of the clumps individually. Use the under 6 items rule to arrange the headings and then subheading below it. It also helps to think conversationally. What would the form look like if you where actually interviewing the user and taking down their answers? This will allow you to see what is important in the “conversation” and what needs to be asked first before later questions make sense.