The answer is as soon as possible, now there are a couple things that you need to know about this process.
First, the film needs to be varsity film, and I’m not talking about just a few plays. A legit varsity highlight tape. No JV plays. And please for all of us, no 7on7 plays. Colleges want to see you perform well at the highest level possible. Not at a JV level. I’m not saying playing JV is bad or anything it’s a good stage for development but a college won’t recruit on that and at the end of the day your goal should be varsity film. Now also, colleges don’t want to look at 20 minutes of “highlights” when they are just regular plays. You need to send in film no longer than 8 minutes at the absolute max. They want to see the first minute and then will probably have a decision made. So don’t hold anything back. If they like what they see they will then request actual game film when they want to watch a lot.
But the main thing is to get out your film out ASAP. Varsity film to colleges you believe will be a good fit for you, not every college in America. Ones you feel you could help out and do your research on them. Make your email stand out. They get thousands of those but if you can stand out, it’s like a job interview. If you leave an impression, they are more likely to remember you and recruit you.