No if anything we are MORE mature:
You might be scratching your head but I'll explain,
Alot of immaturity is derived from social problems between NT's, male NT's are so damn competitive, NT females are so jealous at times, they they do stupid and mean and immature things to each other to hurt each other and then get revenge.
Not saying this never happens to Aspies, but since we are less extraverted, we are generally not inclined to get caught up in all that bitchy drama crap.
We are also not likely to follow the crowd, and can make open-minded and level headed decisions.
Also there is NOTHING wrong with liking cartoons and holding onto childhood memories, I am in some cases like a child, but I am also responsible, reliable, and educated. I am not inferior to NT's at all, I just think differently

I don't know when I start getting too stressed, get really bothered/upset or fall into the gloomy pits of my reoccurring major depression my ability to make level headed decisions kind of goes out the window a little bit or at least becomes a lot harder. I can still make 'open minded' decisions but in that state the decisions I might 'open my mind to' might be terrible.
Also I do not strive to follow 'the crowd' but if I am hanging out with a group of people...I am not going to be vehemently opposed to following along a little bit with the group rather than being contrary about everything. Not to mention I can be terrible at deciding on things to do, sometimes much easier to go along with people who already have some manner of plans. Though I am not going to do something though just because 'all the popular people do' for instance...or because its the latest fad being fed to the masses.