I've posted about younger women before, so I'll keep this short.
I have slept with quite a few of them. 15 (23 or less) in the last 2 years. Only 6s/7s/8s/9s. I'm 35.
(For the most part) they are flighty, flakey, and hyper-emotional. They are also a lot of fun.
The thing I have observed is the problem being an older guy is this: these women are in their sexual prime. The amount of attention these chicks get is almost unimaginable. Facebook, snapchat, twitter, instagram, tindr, etc. But they will see a stable, older guy--that still likes to have fun--as something to go after, something of value.
On the other hand, they get pressure constantly from friends, other dudes, and society in general to continue to play around and not settle down. Often these women will try to lock you down while still playing the field themselves.
So there is a natural tension in these types of situations. Between settling down and playing around.
Best advice I can give is to not take them too seriously. Which helps in two ways: One, a younger chick doesn't want a super-serious older dude. She is still gonna want to have fun in a relationship. Two, she is gonna eventually bring drama and emotionally-fueled behavior to your life. Its inevitable. Staying relaxed about this is the only way to handle it.
As soon as you feel that your life is starting to revolve around their unpredictable behavior, you are in for a world of pain. Its happened to me a few times. And it was very unpleasant. But it was a great learning experience and I don't regret any of it.