When I was most recently single, I said anyone 9 to 10 years older than me was probably too old, wouldn't work... and that changed pretty quickly when I found an awesome guy who's 12 years older. I honestly can't say
I thought I had set my limit, but that was very easily broken. It definitely would weird me out if there was such an age gap that we legitimately just had nothing in common and couldn't even talk about cool old TV shows or something, but honestly I'm not entirely sure at this point!