Hurdler's Stretch = Good? or Bad?

Over the time it will damage it. But you probably won't notice it until you're older.

I recommend two seperate excersizes to make up for it.

One, with one leg bent and the other extended. Use your arms to push the bent knee as far backwards as possible. This will stretch the extra muscles that the Hurdler's stretch gets, without compromising the knee.

Secondly, to get the knees warmed up, stand up with your feet together, and bend them as you rotate in a circle clockwise, then straighten and repeat counter clockwise, back and forth several times.

If that doesn't help the muscles you're looking for, just tell me, and I could mention some other stretches.