It pops into my head from time to time. I feel very fortunate for everything that has led me to this point, were I to learn that I had days left, it would be upsetting but I'd feel like I definitely had done some living and that had been satisfying (not necessarily the happiest guy in the world, but I have had some good times and known some wonderful people).
I think it is good to keep it in the back of your perspective and consider it once in awhile. As we get older, the years tend to just shuffle by - I remember being a young man and visiting my then-girlfriend's great uncles, who were living together. Of course I'd been around old people before, but that was the time when it solidified in my head "they have been living in a static situation for YEARS." And then of course moving to the city and noticing elderly people sitting at bus stops at strange times, that sort of thing. The thought of all these people just existing for years upon years upon years, going through the motions of their lives. Work, grow old, retire, steadily falling apart. It started to register with me and I think about that more and more as I myself age.
I guess in my usual rambly way I am trying to say, the time we have here in the world is so precious. And should we make it to some peak part of our life, that also particularly precious because at some point you will start feeling yourself and your life fading away. All of that is natural, but it is important to keep things in perspective and make good use of your time, energy, and resources while you can. Otherwise, you are just locked up in a box somewhere & waiting for your expiration date, and then that is that.