I'm in a relationship currently and haven't looked in 7-8 years but hard cut off is obviously 18 (probably more like 21 though). I'm not going to not give someone a chance just because they are a few years younger or older than some arbitrary number.

But realistically I'd want someone close to my age with similar experiences. There's an inherent connection to be made with someone that grew up watching the same cartoons, having the same toys, seeing technology grow during roughly the same stages in our lives, etc.

I'm soon to be 35 and if I suddenly found myself single, I wouldn't immediately turn down someone +/- 10-15 years of my age. I fully agree that it's objectively weird and creepy and would probably feel some shame if I were to try to bring home a 21 year old, but some people you just click with. Though you may always learn that, hey you two are in completely different stages of your respective lives and you just don't have as much in common at you first thought and it's probably best to move forward separately. That's just part of life.

Sorry for the ramble, it's late/early and I'm still reeling from the time change and in a weird mood unable to sleep.