On my house

I live in the house that my parents' owned before me. My family, in one form or another, has lived in this house since 1984. That is 25 years. And in that time, there have been almost no significant changes. It is likely that my wife, family and I will live in this house for a while...I'd guess a minimum of 20-23 years (approximate time for my youngest to get through college).

So, if you were living in your home from childhood and you could change things over a period of time - what would you change first? In addition, if you knew or suspected that you had a 20 year window to make these changes - would that impact your thought process?

I find that there are things that I'd love to change - such as adding a bathroom in the basement and a wet bar or having a library or more space with fewer rooms. But, when you know you pretty want to re-do everything but keep the continuity the first couple of steps are really challenging because you don't want to destroy the existing heritage. So, how do you keep the essence and character but slowly evolve the place to be more usable.

My immediate thoughts are better efficiency - windows, lighting, insulation, roofing and a bigger water heater. However, I am open to other people's thoughts. What would you do if you were in my shoes with your own childhood home?