It really depends. Because of my personality and life experiences I was done at 12. Only 1 or 2 of male friends stopped being immature in high school. The rest are still growing. I would say maturity is a measure of experience and how one personally handles things and not a measure of age. You can definitely help him mature quicker if you are patient with him. Your example alone might be in enough in time assuming you are around him enough. Even without you he will make some good advancements in the next 2 years.
Like never, we are failing evolution it's all good, I said it before I'll say it again, the fucking Dolphins are going to take over here soon because they are out-evolving us, watch it'll happen guys, just watch
At the same age women grow up and act mature, never. You are as immature as he is no and ifs or buts about it. Just because your immaturity looks different then his doesn't make it any less mature (guys like joking around women like drama etc etc). So stop expecting him to suddenly stop being him and start acting like you because thats not whats going to happen. He isn't going to suddenly stop being immature so that he can be the ever so mature person that you are and gossip about othe people (yes I am making an assumptiong but I am doing so to make a point). He is who he is you are who you are and you should except that fact. I find personally that women who embrace a mans immaturity are actually much happier then the ones who don't because its a part of every guy its who we are and its kind of part of the charm.
Just because you have a certain expectation doesn't mean that someone else has diminished intelligence. to be honest... guys are way more smarter than girls... for one.. we don't have expectations.. we deal. so how about you stop acting like a little kid? Guys will always be guys darling... just grow into the woman you will be and stay a woman and im SURE a MAN will come up to you and then you can consider if he is a kid then or not.
There no set age. Not all guys act like children and so you can't really lumpsum them all into a naturally lifeling immature category everyones immature to a certain extent there entire lives. Just depends on the person. But you can't divide this into just guys. Women can be just as immature. And everyone can revert back to it at any given point.