This is an interesting discussion. Allow me to take part. I also have age preference in a range of few years, however, I also have a friend who says that she likes someone much older, say 7 - 10 years older. And one of my best friend also married someone who is 11 years older. So I think it's all about preference, how you have formed it in your mind since you were young. I just knew it after these friends revealed it to me. As for me, after debating it for quite a long time, I go back to where everything started, my own preference, but giving a bit wider range this time.
Nowadays when people introduce me to a guy, the age difference is always big. When I ask why, an old relative explained that if you're still 25 for example, 8-10 years difference would mean the guy is 33-35, which usually still looks young. But when you do the same math for age 35+, of course you'll get 40+, maybe up to 50. That's why I feel frustrated sometimes.
Another thing is that recently a woman told her story about how she and her daughter have been praying for a soulmate for her daughter. Her daughter made a list, a detailed list, of the qualities that she wants in her soulmate. I think the list is very very detailed. And she got it ! exactly as she wrote.. Her story somehow evoked me, and I wondered whether we have to tell God exactly what we want. But really, in a very detailed way, including age range, so that He doesn't send us wrongly?