32-year-old guy dating 23-year old girl - is nine years difference too much?

I know age shouldn't matter, but I've known some young girls (maybe a year or two younger than that) who are pretty immature. This girl, she's lived on her own for a while, is finishing up her undergrad in the spring (while working two jobs), and will then move on to her Master's right after; in other words, she seems to have her head on straight. She's not into heavy partying, clubs, or drugs; she's a very polite Southern girl who seems to have good family values. She's never been married and doesn't have kids; I've never been married either (focused a lot on school and work).

I don't get an immature feeling from her (haven't known her that long, though), but I've usually dated girls/women closer to my own age. Has anyone dated someone with a large age difference like this and had either a good turnout (married?) or at least had some good stories?
32-year-old guy dating 23-year old girl - is nine years difference too much?
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