Age really doesn't matter once you're both adults. The thing that people tend to forget is that the thing that matters is the maturity level. I've met people my age (40 somethings) that were childish and 18 - 20 year olds mature way beyond their years. The group that is so set on age being such a big factor is forgetting that the number means nothing. Some might say "well a 20 year old doesn't have the life experience that a xx year old has..." But I ask this question in response to that: do you think that just because someone is younger, that they couldn't have had the experiences an older person would have? Think about a younger person that has been through the wringer in life and compare that to a 30, 40 or even 50 year old that has had a life of ease... I could go on explaining what I mean but I hope you get the gist of it from this.

Don't worry about it, if you both get along great and your relationship is good, that's all that matters.