Questionnaire Versions

Can anyone point me to documentation or give me an explanation how teams are implementing versions for Questionnaires in their projects?

I have been reviewing the question library and several of our questionnaires.  I can see that there are options to add hide/show rules for a single questionnaire and it seems it would be possible to create questions in the library for "year", as an example.  Then, I could add rules that when the assessment is created and a variable is x, then use the 2014 questions vs. 2013 (again as an example).

However, it seems to me that this could become a nightmare viewing and maintaing after several "years" (aka several revisions) considering you could have over 100 plus questions.

However, what if I'd like to just create a brand new questionnaire from scratch... To give some background, we have 2 questionnaires that I want to merge into one and would rather start fresh than revamping one of the existing questionnaires.

I realize that our target app has a lot of calculations that we will need to update in order to pull data from the new assessment, but I haven't seem to have found how other teams have addressed this in their designs.

I have watched one of the weekly training videos on questionnaires and question library but it didn't seem to address versions, only adding new questions.