Here's my Oprah speech for you:
They say "birds of a feather flock together," right? Well more often than not, the people we tend to spend most of our leisure time with are the people who are most like us. I think this is because friends inspire each other. Sometimes, however, it is simply the case that our friends are like the people we once were. Perhaps they have not changed whereas you have, and perhaps they have not been inspired by your change. Even more rare is a situation where your friends were never a good fit for you! In any case, if you think your friends are less mature than you, you have to ask yourself a few questions:
1) Am I actually more mature, or am I just ranting?
2) Did I outgrow them? Am I noticeably the most mature person in the group?
3) Are our differences truly a detriment to my personal growth? to my relative happiness?
1) Take a GOOD look at yourself. If you aren't really more mature than your friends, but are merely ranting, then shame on you for suggesting there's something wrong with them. If you actually are, my advice is don't burn bridges...but don't hold on to chains!
2) If you're not noticeably the most mature person in your group, return to Question 1. If you are, perhaps you need to be more astute to your standards and morals. Think about what annoys you and why. Let reason and ethics guide you, so that you can be fully equipped to help your friends (or anyone else) understand why the way they behave is inconsistent with your standards and morals.
3) If your differences with these friends don't truly make a negative impact on your life, again return to Question 1. If they do (or even if you are not sure), try what some of the other RJers have suggested and spend some time with other friends you think are more mature. See if you fit in. Do they share most of your standards and morals? Are you more comfortable?
The bottom line, in my opinion, is if your friends are simply slow to mature it is your duty as a good friend to help them understand where you stand. If they cannot accord with your new direction in life... stay in touch, be cool, don't lose a friend, but don't get tangled in their mess!