After today's chapter some people thought Sasuke's technique required start-up time because of this scan, which is actually incorrect:
The next page after you see Sasuke using a hand sign; indicating he is charging up his chakra to use Amaterasu not his teleportation:
As seen here, Obito stated he had sensed Sasuke charging up his chakra into his left eye:
During the fight with Madara, Sasuke used his teleportation back to back roughly 1-4 times. Though he didn't spam it, he still used it a significant amount of times to show he could use it whenever necessary.
1.
2.
3.
4. He possibly could have used continuous teleportation to get within range or it could have just been just raw foot speed
To conclude, if Sasuke's technique required start-up or needs to be charged it would mean he couldn't use it back to back as effectively as he did against Madara.
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The next page after you see Sasuke using a hand sign; indicating he is charging up his chakra to use Amaterasu not his teleportation:
You must be registered for see images
As seen here, Obito stated he had sensed Sasuke charging up his chakra into his left eye:
You must be registered for see images
During the fight with Madara, Sasuke used his teleportation back to back roughly 1-4 times. Though he didn't spam it, he still used it a significant amount of times to show he could use it whenever necessary.
1.
You must be registered for see images
You must be registered for see images
You must be registered for see images
You must be registered for see images
To conclude, if Sasuke's technique required start-up or needs to be charged it would mean he couldn't use it back to back as effectively as he did against Madara.