Can a guy and a girl get along if they both have the same personality?

I don't get it. Does that mean you're annoying and needy?

As far as a long term romantic relationship, it is challenging. If you and she share the same characteristics, then you basically end up dating your self. No one wants that.
You begin perhaps to see your flaws, you always know what is coming, and if you are truly identical in thought patterns, you know what they are thinking all the time. Which leaves no room for conversation.

It is a very cumbersome relationship to have long term.
Check my behavior article on the Personality Synthesizer for more information about this topic. (little bit of self promotion)

Can work out, if either one in the relation is fine with negotiating. But over long term this wouldn't stick. Does give you tremendous leverage over other couples in terms of both looking at basically the same arenas of entertainment, saves you the trouble of understanding her.

But as I said over time, this may bore. Cause both would be too predictable for each other :-)

Depends on the personality, if you both are needy and must have it your way. That relationship is going to be a big challenge, unless you both accept who you are and try to work it out, it won't go far. If you both have a nicer/calmer personality then yes it can.
as far as age being a factor. Id say no. Because I've gone out with plenty 18-22 year olds and they are mature, still playful and what not , but won't act like brats.
ive met 29-33 year olds and they acted like brats, so I think it all depends on how the girl was raised, and who was/is friends with. Can't just assume all young girls are annoying and needy.