How often should I stretch? Daily, twice daily, four times a week? When? I usually stretch five times a week just to prevent injuries.

Obviously stretch before every practice even if your late. Don’t pick up a ball until you think you have completely stretched yourself out.

After pitching whether its bullpen or live I always like stretching over again as I feel it reduces recovery time and soreness the next day. I also stretch after weightlifting.

Actually, you should do a dynamic warm-up before practice/games and stretch afterwards while you’re still warm - it’s better to stretch warm muscles than cold muscles.