The Big Questions

Last night I spent several hours with Dad while Mom went to see one of my nephews graduate from high school.  We talked about random topics ranging from the boat Mom & Dad owned before we were all born to how well my Dad is getting around these days.
Whenever I sit with him I'm aware of the ticking clock in a way that makes me feel like I should be discussing "the big questions" of life with him.  The problem is that I'm not sure what those are.
On the one hand, we've talked throughout the years about how my parents met (high school bus) and their first date.  Actually it was their third attempt at a first date.  For the first two attempts, Dad ended up in the hospital for surgery on his ear and then an appendectomy.  We've talked about why they married in November when the original wedding date was in June.  Not surprisingly, my paternal Grandmother was the problem with the June date. 
We've talked about things like why he loves hockey.  We talked about why he didn't pursue a professional baseball career.  It didn't pay enough.  He had a chance to get a good union job and marry Mom. 
We know they don't go to church because religion was a huge problem when my Catholic father married his Presbyterian bride.  My paternal Grandmother harped on that until she died.  Well into her nineties Gram was still upset that Mom never became Catholic.  As a result, my parents didn't raise us to practice either religion.  They still won't go to church for anything other than official events like weddings, communions, funerals. 
Last night Dad talked a lot about life before and after children.  He started by talking about how much our twin daughters have changed our lives.  He moved into talking about the wait to bring me home from the hospital.  I was born just before President Kennedy was assassinated.  The whole country shut down for a week to mourn.  This was a huge problem for a couple waiting for the courts to finalize the adoption of their first born.  Dad said Mom didn't sleep all week and that she about drove him crazy.  I can totally see that happening.  Mom develops a level of Type A anxiety that few can match, except perhaps her daughter.  
He told funny stories about (finally) bringing me home and surviving the first year.  He talked about how glad he was that we had the girls.  It was an interesting and easy conversation that he completely led. 
I feel like the clock is ticking and I should be asking more questions, but I cannot figure out what else I want to know.  I'm so afraid that by the time I figure out the questions it will be too late to get answers from Dad.