You are right, none of us know how much longer we will live, and as time passes we do tend to become more aware of this.
I am 72, so here is some hints based on what has happened in my life in the ten or so years I am ahead of you.
Discuss, if this is at all possible with your husband now, whilst you are both well.(You are, and I hope he is too, )what kind of funerals you want, whether you want to be kept alive as long as possible, if you are willing or not to denote organs after death.
Make or revise your wills - both of you.
Make provisional power of attorney for you both, so some younger person will accept responsiblity for your welfare if either of you should be unable to decide for yourself at a later date.
A pre-paid funeral plan is a good idea too.
Then the more joyful aspects of retirement:
DO the things you have dreamt of through the years, if they are at all possible.
We sold up, bought a boat and sailed the canals and rivers of Europe for three years (DH's dream) when he was 57 and I 61, then bought our present house,. And I am so thankful that we did as last year, ten year's after fulfilling my husband's dream, he is in his grave - something thankfully, neither of us had thought likely in 2013.
So don't put off til tomorrow, what you can do today. I hope and trust that you both have much longer than ten years ahead of you, but as you yourself say, we do not know that.
Don't worry unnecessarily, or let gloomy thoughts dominate - enjoy this time of your life!