Looking at your product for a long (200+ question) business evaluation that requires a member to purchase before accessing.
It's hard to confirm features with the majority of your site behind the license access, but I wanted to confirm:
1) it can handle a multi-page script
2) Using a membership ecart like Cart66 or Shopplugin I can restrict access to the forms
3a) a respondent can save and return to a partially completed form and resume it (2 hours can be a long time to complete the survey)
or
3b)If they cannot save a partial form, I can break the questionnaire into multiple forms and allow a member to only complete each one once.