My current partner is seven years older than I am (36 to my soon-to-be 29). I think that's enough of a gap.

I've dated people that were significantly older than me, including when I was in my teens. I look back on it now and I'm unsurprised that the relationships I had with them were abusive—because it's impossible to have a relationship of "equals" when you're 28 and dating an 18-year-old. I don't think every older/younger relationship skews that way, but as someone who is in their late 20s, I can't fathom dating a teenager. :|