system
A chat on subreddit /r/NoStupidQuestions
human
If the older guy is less mature than the younger woman, the long term prospects are poor. She will probably tire of him when she realizes he’s never going to grow up. He will tire of her demands that he grow up.
gpt
There's the question of whether it's down to slow development or delayed development. For example, if the older partner struggled with a drug addiction or mental illness and it took ten years to get sorted out, and now they're ready to buckle down and start a career, get married, and have kids, they might be a good match for someone younger who's at that point.

Related, it also matters what we mean by maturity. Whether you're at similar life stages is important, whether you giggle whenever you encounter the number 69 isn't.

Always. You should always giggle when you see or hear that number.