Depends on the people and personalities involved.
Lets deal with the obvious issue first - its very likely he will die before you. Possibly by a good 20+ years. Yes, I know you could get hit by a bus tomorrow but you have to deal with the most likely outcomes.
This facts means you have to think about the money issues. You may be financially independent. Good for you if you are. If not you both need to spend some time considering the future.
Then you have to consider that you may have a long period at the end of your life when you are alone. Do you think you can cope with that?
Are kids on the cards? Hopefully not, as men in their mid to lates 50s don;t tend to make good parents. Most do not have the energy to raise a child who is almost two generations younger.
My Dad's 15 years older than my Mum. They were OK til he was 70. Then he had a number of health issues - strokes, generally stuff from being 70. My Dad socialises less and less. Some of his mates have now died and he looks to my mum to basically keep him entertained all the time. It is driving my Mum nuts - literally. Some of the behaivour is down to my Dad's personality, which was not obvious when he had a wider circle of friends and interests.
My mum, rather than having a relaxed time in her 60s, having grandkids over and that sort of stuff, is having to entertain my Dad. He kicks off when grandkids turn up and takes attention from him.
My mum has stopped traveling as she finds the price of travel insurance too high.
Frankly, choosing an older partner has made my Mum's old age a miserable and unenjoyable.
Yes, someone in their 50s can be energetic and good fun + company. But most people age rapidly once they get over 70.