Elisabeth - Sorry, I wasn't clear. I agree that maturity doesn't always comes from bad experiences. First off, many people manage to live through experiences and not seem to gain any maturity at all. But for the rest of us, we learn from our experiences - both good and bad. Neither my husband nor I dated a lot before we met, but I do think our experiences shaped who we were and particularly who we were with each other. My husband's dating experiences were more stereotypical - not awful, but rather standard, whereas most of my dating experiences were positive and ended well - I mean, obviously not in the best possible way, but I was still friends with my exes when I met him.
More than that, though, I think other experiences also made us more mature. Again, not necessarily bad experiences, but just having lived life more than we had when we graduated high school.
I don't think Lois and Clark necessarily need bad experiences (which isn't to say they may not have them), but I think there are still things they need to learn. Even Clark's learning to deal with Steve is a learning experience that may help him deal with others better in the future.
While I'm not planning to get us through to their mid-20s (I'm actually not planning to go past their freshmen year of college), I expect both Lois and Clark to be much more recognizable as their older selves when we finish. I just don't think they are there yet and I don't think they would necessarily get there as quickly together right now.