This.
I strayed from this formula by 1 year once (I was 38, she was 25), and there was this strange generational gap where we just had completely different interests, we didn't get each others' references, and things fizzled pretty quickly.
Anyone else I've dated has been within this formula and we've gotten a long quite well. If they're below this number for you, or you're below this number for them, even by a little bit, it'll get weird and you'll run out of things to talk about pretty quickly.
Yeah, the farther away you get from your own age, the harder it gets to find a relationship that works for you. However, straying from that formula, even a little bit, seems to be a guaranteed breakdown point.
The woman I'm seeing now is three years younger than me, and we work incredibly well together. Gonna keep this one, I think ๐