Users cannot change their previous answers once a questionnaire has been submitted. If they save a work in progress, they can change answers until they submit it. But the results are not available to anyone else until they submit.
By "inconsistent", I mean the overall data results. If some users have answered one set of questions, and then you change or add/delete questions, the users who answer after that have different structured data. That makes it difficult to do any kind of analysis on the overall results.
mike