My boyfriend of one and a half years is a little less than four years older than me. We met when I was sixteen and he was twenty. A lot of people frowned on it, but I never saw it as an issue.. before that, I had a seven year age difference(that one was a little weird simply because I was in high school) and a three year one(thirteen to sixteen). I'm not sure WHY it's taboo, but I guess some people just see it as strange.
The older you get, the less it matters.
The older you get, the less it matters.