Should you put the weight down once you reach 10 rep, or when the muscle starts to feel uncomfortable or when you can't do any more reps with good form? (fitnessandpower.com)
To gain quality muscle over the winter months, try to follow this rule: When you can't do any more reps, do two more! (gymjunkies.com)
If you can easily do more reps then it means you should increase the weight to make it more challenging! (fitbodyhq.com)