What's the biggest age difference in any relationship you've been in?

I'm 34M. For me, it's 5 years, I was 31, she was 26, didn't go well. No life goals, just asking for money and planning trips. I met this amazing 24yr old 3 months ago and she just makes my days. Very mature and hard working. I've been giving myself a hard time over the age difference especially since my sister is 28. My friends see no issue, since she's very mature and has her master's already. I'm not sure how to proceed.