Portfolio Design Refresh, How Far is Too Far?

I’m concentrating on developing and improving my existing WordPress theme portfolio rather than/before I develop any new themes.

A couple of my themes I’m going to re-develop entirely using my new framework and plugins so that my entire portfolio is consistent and much easier to manage and while Im at it give them a design refresh/update.

My question really is how far is too far when it comes to design refresh/improvements, where do you draw the line (obviously a complete redesign is well over the line or is it)?