Are our heroines growing up?

Recently I've read a few NA (New Adult) books and enjoyed them thoroughly. These are book featuring young heroes and heroines (usually in their early 20s) and targeted at readers roughly the same age.

However, when I first started reading romances, early to mid 20s was a pretty standard age for most romance novel heroines.  These days there seems to be an an increasing trend in contemporary romance (and especially in erotic romance) towards older heroines.

My own heroines tend to be in the 28-33 year age range, because I prefer slightly more worldly-wise characters (no simpering virgins here!)

It's made me wonder whether (a) it's only a trend in my reading rather than the world at large, (b) it's a new trend caused by the split between NA and contemporary romance, or (c) it's a growing trend because readers are growing up and looking for more mature heroines.

So it's poll time! Please share your thoughts in the comments, and take part in the poll in the right side bar to let us know (as readers rather than as writers) which age group you prefer your heroines to be.