I'm dating a guy six years younger than me..plz help?

hi i'm 27 and dating a guy who is 21. He's very mature for his age and understanding. He's family seem to approve of me even though they have't met me. He cares alot about me and is very serious bout our relationship. I know this is not the typical situation, but i was thinking will he leave me for another woman when i hit my menopause. cuz he'll probably only be 44-45. what other problems might we have?