Each person who will be of the age of eighteen years or more at the next ensuing November election, who is a citizen of the United States, and who, if he continues to reside in the precinct until the next election, will at that time have fulfilled all the requirements as to length of residence to qualify him as an elector shall, unless otherwise disqualified, be entitled to be registered as an elector in such precinct. When once registered, an elector shall not be required to register again unless his registration is canceled.