I worked with a guy in our association last fall who was 69. Good rules knowledge, good game management, good guy. He just couldn't get up and down the court and keep up anymore.
Two year's ago I was on the court with him as the T and he was the L (three man) and on a long rebound I saw him get tangled up with a big kid who knocked him down going for the ball (he just couldn't get out of the way fast enough). Tore a tendon.
Similar to me (50), the mind is willing, but the flesh is weak...... Hopefully, I'll know when to hang it up.