I recently attended the LDStorymakers Conference and received a recommendation from a couple of authors that I increase the age of my main character (it is a romance novel). At the beginning of my book, she is 19 but the bulk of the book transpires when she is about 23-24. What age range would you recommend? Is 25 still too young? Thank you.
I generally don't like to have a character introduced at one age, then jump forward in time five years to where the story actually takes place. You can sometimes get away with this in fantasy by using a prologue, but prologues aren't really the "in" thing right now. Maybe it's tolerable if something happens to the character as a very young child, and for some reason it needs to be described in real time, and then you jump ahead 20 years. But even then, it usually is going to be better to start the story at her current age, then fill in the backstory at appropriate intervals.
As to what age your main character should be, it depends on the story you're writing. Teen romance is fine, if it's not explicit or too sensual and follows LDS dating standards and guidelines. Romance in your early 20s is fine, and generally this is when most LDS girls fall in love and get married so I don't see a problem with it.
Not knowing anything about your story, I can't say why the authors thought your character needed to be older or if they are correct in that advice. But if those advising you are successful published authors in your genre, I'd probably listen to what they had to say.