I lost my father when he was barely into middle age. That was nearly 25 years ago and I think of him often and remember him in most everything I do. My family knew as you do that he had a short amount of time to live. We all spent as much time as we could with him talking about everything imaginable including and very importatntly his passing. I think it is so very important to tell a loved one such as your father that you do love him and to also say goodbye. Pull out pictures, ask many questions you want answers to, who was he growing up, etc, etc. Soon God will take care of him for you. Your family will be in my families prayers.