Integrating followup Survey..er,I mean Online Petition via webform civicrm

[sonicthoughts]

Any suggestions on the right approach here:
Organization has a seminar and wants a pre-event survey and 3 followup surveys with basically the same questions to gauge lasting impact.  Each survey has 5 groups of 12 questions in form of point scale from 0 to 5 (Agree, disagree, etc.).  Survey also has demographic info which is asked initially and associated with the contact.
The contact info can be stored in civicrm custom fields or webform fields and that is not a problem.
The issue is how to track the same profile questions stored by activity.  I have not figured out how to use petitions but it seems these are activity fields but I was not able to have then change per activity - they seem to track to the contact.  therefore the 6 month followup would overwrite the 3 month followup.  Would this be solved using activity and campaigns? 
Furthermore, I'm not sure how to integrate this all into civicrm-webform.  With 70+ questions and rating questions - does it make sense to store all this in civicrm or would webforms be a better solution?  If so, is there a way to pass any information back to civicrm so we can create a report?

Would appreciate some direction from any folks who may have run into this in the past.

[Coleman Watts]

these are activity fields but I was not able to have then change per activity - they seem to track to the contact

Can you ensure that the custom fields are extending "Activity" and not "Contact" or "Individual"?