Connectives with a parallel series should be repeated when clearness requires

From the Century Handbook of Writing (1919):

37. Connectives that accompany a parallel series should be repeated when clearness requires.

Preposition to be repeated: He was regarded as a hero by all who had known him at school, and especially by his old school mates.

Sign of the infinitive ["to"] to be repeated: He wishes to join with those who love freedom and justice and to end needless suffering.

Conjunction to be repeated: Since he was know to have succeeded in earlier enterprises, though confronted by difficulties that would have taxed the ability of older men, and since his powers were now acknowledged to be mature, he was put in charge of the undertaking.