Meh, as long as the youngest one is of legal age I try not to judge factors I am only partially privy to.The younger one could be wiser than their years while the older one completely immature.If there's one thing you learn from being older is that time flies.
I have personally observed a shift in most women around 25. If she were 25 and you were 33, no problem, but I'd hold off on this one.
They are out of college, they have some real world experience, etc. It's not the age difference so much as it is its location on the time line.
For myself tho, I wouldn't date anyone who couldn't go to the same places or participate in the same activities as myself. If you are on the same level, it can work out great.
Being over 21 and dating someone under 21 just seems silly to me. Turned out I was emotionally more stable than he was. Another often overlooked factor is that she will NOT be 18 or 19 forever.
I am sure there are exceptions, but in general, the age and maturity levels are too far apart at this time for them to have a high probability of success in a long term relationship.