When it comes to longevity in the weight room and on the field, not getting hurt is key. And while it's mostly anecdotal evidence, the athletes and clients of mine who perform dedicated stretches – especially the hip flexor stretch – prior to training and competition tend to not get hurt.
Real vs. BS Hip Flexor Stretch
To be more specific, do a REAL hip flexor stretch, not that BS one you see most people doing where all they do is extend through their lower back and defeat the whole point of the stretch anyways.
When you stretch in excessive anterior pelvic tilt, you're not stretching your hip flexors. You're stretching your lower back. Also, the same people who do the stretch that way will always complain of feeling tight in their hip flexors.
That's not tightness, that's you plowing through the anterior hip capsule, forcing the femur forward. That's protective tension you feel. And that shitty hip flexor stretch you're doing is only feeding the issue. Besides, you'd think after several years of performing that stretch something would have changed by now, right?
A hip flexor stretch doesn't entail crazy ranges of motion. Get into the half-kneeling position and then squeeze the glute of the side that's on the floor. Think: belt buckle towards chin. This will posteriorly tilt the pelvis. Now scoot forward maybe an inch or two, moving through the hip itself and not your lower back. That's a "real" hip flexor stretch.