That depends, of course, on the role and the script.
Vivien Leigh, for example, had an absolute memory.
She was able to memorize 7 comedies and dramas by Shakespeare, totaling over 1000 pages of dialogue.
She had an incredible ability to memorize all the lines of a play after reading it only once.
In his book "On Acting" (1986), Olivier said that when Leigh was in one of her "moods," she needed two readings.
She was the best Lady Macbeth he had ever seen.