Question: How long does it take for the Bodhisattva to be able to plant [the karmic causes which result in] the thirty-two marks?
Answer: The very slowest is one hundred kalpas. The most rapid is ninety-one kalpas. As a Bodhisattva, Śākyamuni cultivated the thirty-two marks to completion over the course of ninety-one great kalpas.
This is as described in a sutra:
Long ago, far back in the past, there was a Buddha named Pusya. There lived at that time two Bodhisattvas, one of whom was named Śākyamuni and the other of whom was named Maitreya. Pusya Buddha wished to observe whether or not the mind of Śākyamuni Bodhisattva had reached a state of complete refinement. He then contemplated and observed that although [Śākyamuni's] mind was not yet completely refined, the minds of his disciples were all thoroughly refined. On the other hand, although the mind of Maitreya Bodhisattva was entirely refined, still, the minds of his disciples had not yet reached complete refinement.
At that time Pusya Buddha deliberated thus: "The mind of one single person may be easily and rapidly transformed whereas it is difficult to swiftly heal the minds of a multitude of people." After he had deliberated in this fashion, Pusya Buddha wished to influence Śākyamuni Bodhisattva to rapidly realize Buddhahood. He travelled up onto Snow Mountain and, inside of a bejewelled cave, entered the fire samādhi. At that time Śākyamuni Bodhisattva was a non-Buddhist rsi. He climbed up the mountain to gather herbs and discovered Pusya Buddha sitting in the jewelled cave absorbed in the fire samādhi and radiating brilliant light. When he saw [that Buddha], he became delighted in mind and, out of faith and reverence, stood on one foot, placed his palms together and singlemindedly contemplated him. For seven days and seven nights [he stood and contemplated like this] without blinking his eyes and then uttered a verse in praise of the Buddha:
Up in the heavens and down below, there's no one like the Buddha.
Throughout the ten directions' worlds, there are none who could compare.
For I have seen all that there is existing in the world.
And nowhere is there anyone who ranks as equal with Buddha.
For seven days and seven nights, without blinking his eyes, he unwaveringly contemplated the World Honored One. He was [thereby able] to skip over nine kalpas so that after ninety-one kalpas he realized Anuttarasamyak- sambodhi.