I'm 40 and my dp is 55, nearly 56.
He is fantastic. Full of energy, strong, sexy (absolutely no problems there at all
), hilarious, loving, romantic...I could go on but I'd bore you.
When we met, I fell in love with him very quickly. His birth certificate didn't really come into it. I'm not saying we didn't discuss the gap, but honestly, all the discussion in the world would not have changed my mind. I adore him, and I honestly couldn't give a fuck how old he is. He's a person, not a date of birth.
If he becomes ill or infirm, it'll be my privilege to look after him, because he's the love of my life, and that's what you do for the person you love. Just like he would for me.
As has been said above, there are no guarantees that your partner will remain in good health, no matter what the age difference between you.
All we have is today. If you're lucky enough to be able to share it with someone you adore, then for goodness sake embrace it.