Less is more! Many people “over-practice” thinking that it is helping them.
If the voice gets tired, the external muscles will take over and cause you a myriad of problems. Stop practicing before you get tired. Less is more! Only practice as long as you can stay mentally alert and physically fresh. Singing on automatic when practicing is extremely detrimental. It not only reinforces your old, bad habits, but also tires you out vocally! Obviously, different singers with different voices can sustain varying lengths of practice.