The other side of age.....

When is "too young" for certain roles, etc.
This is the other side of the age question....What if vocally and dramatically you feel like Marcellina, Katisha, Berta, Quickly, etc. but people want to cast you as Cherubino, Pitti-Sing, Rosina, and Meg Page? Well, you may have to face that fact that you are those lighter roles, or, you may have to hope that a perceptive director, conductor, etc. will see that you really are that character singer, and the fact that you are 30 shouldn't be an issue. You will notice that I gave a female example. It does seem like there are more examples of young tenors and bass-baritones doing "older" character roles than women. There are, of course, exceptions to this rule, and unfortunately this can be a steep hill to climb. Unfortunately, it seems like the only people who can make this work are those who are considered to have a "quirky" look, or are of stouter build. This is unfortunate, because make-up and costuming can create the same effect.
An amusing counter-point to this is running into (particularly male) singers who are having incredibly busy careers that most people would kill to have, but who are nonetheless unhappy because they've been pigeonholed in character parts!
To get back to my original point here, if your interest lies in character parts, and you don't fit the classic profile, you will need to do some PR and promotion work to be seen in that light. However, if you can pull it off, you may find a rich career path that many don't consider.