I was recently asked the following question:
How much does age and experience factor into getting started in Hollywood?
If you are looking to break in as an assistant to a producer, studio executive or agent, it helps to be young. In reality, most adults would not want these positions. These are the types of jobs that young people are more willing to do since the pay is low and they entail a lot of grunt work, which is fine when you're just starting out and if you have the means to sustain yourself. In some cases, young people have parents who are willing to subsidize them in these jobs as they realize it's an investment in their children's futures...or younger people are willing to work night jobs such as bar tend to make ends meet, concessions many adults are not willing to make. Assistant jobs are a rite of passage of sorts and can provide invaluable experience. But it is not essential to have this experience in order to make it in Hollywood.
Specifically when it comes to screenplays, I don't think age is such a factor since what matters most is the content. If you have a great script with a great concept that can get noticed by people who can help get your movie made, age doesn't really matter. If someone is young and writes a crappy script, no one is going to buy it just because they're young. And even if someone is 25 and brilliantly talented, their age won't guarantee that their project will get noticed. It's a tough business no matter how old you are.
What matters most is having a great story that's well-executed.
It's content, not age, that's King.
No matter what your age, your focus should be on creating a great piece of work and having the wisdom and self-honesty to know what's good and what's not.