Yes, you go on until you're at death's doorstep or until you destroy your voice as Miss Andrews did.
Never having been in a musical before, even in a featured role. Lauren Ambrose probably did not know how difficult the role would be for her. Admittedly, she might have gotten an idea from, for example, Kristin Chenoweth in On the Twentieth Century. With all her training and experience, Chenoweth still told all that she had to live like a nun while doing the role, and was rarely heard speaking any louder than a whisper when away from the theater.
But isn't it really the responsibility of the director while casting to choose someone he or she believes will last the role? And to make certain that the one to whom the role is offered understands the hardships?
I heard a lot about Laura Benanti, who is a favorite here. When I finally saw her in She Loves Me, I didn't think anyone could have played the role better. But this didn't lead to a flood of producers and directors at her door. The problem is too much talent in New York, and not enough places to showcase it. This leads to a lot of bad feelings.