Useful training?

I recently decided to start warming up my arm for the baseball season. I set up my net at the top of the my driveway (about 50 -60 feet long) and I get a small hockey net and throw into it, the driveway is on somewhat of an incline, but not to the point where I am throwing way to high. Basically, every time that I throw a pitch that enters the net, whether it being a fastball or breaking ball or changeup or whatever, if it is a hard thrown/good pitch, it counts as a pitch, and I count up to 100 good pitches. Is this worth it/dangerous/useful etc.

(btw I am sixteen and have been throwing for a long time, and I wasnt really sore the day after throwing the ball)

I generally throw from 70-100+ throws a day. On days when I don’t have someone to throw with, I throw to one of those target net things. I also throw to a target (shoe, cone, etc) a certain distance away for long toss when I’m by myself.