How Long Should You Hold Stretches For BJJ?

Is holding a stretch for a shorter vs. a longer duration better or worse? How long to hold a stretch before exercises? How long should you hold a stretch after working out?
I go into what has worked for me over the years as a BJJ practitioner and what I felt was effective when treating patients as a Physical Therapist.
The goal is to stay injury-free, help with recovery, and stay on the mats.