I'm 8 (and for 3 months in the year, 9) years older than my dh - we have been together for nearly 15 years, have 2 kids, known each other for 18 years.
I'm in a different situation than the OP, as I was very naive and immature for my age when we first met, didn't have children and didn't consider myself any older than him. I have also always looked a lot younger than my age and still do.
Nobody can tell an age difference (yet - hey, I'm a realist) but then, we also seem a lot younger than our contemporaries - they call us kids, even though we are in the same age bracket as them.
As we get older, the appalling truth of the actual numbers seem to correlate less and less with how we feel on the inside :)
I couldn't imagine being with a man older than my age, as it would seem like a 'father figure' to me, (I lost my own father as a young teen - maybe that has something to do with it), and I still have that 'I'm not actually a real adult, I'm an impostor' feeling quite a lot.
In summary, all of the above, plus being very compatible in life goals, lifestyle, music and comedy tastes, is why it works in our particular situation.