What yall should consider is that the more one uses a technique the less chakra taxing it is for him/her, it was stated back in part one, and as seen with sasukes chidori, kakashi been able to use kamui more times, SM naruto using more than 3 rasenshuuriken etc, so I'm guessing in boruto the movie its less chakra taxing than it was in gaiden (despite not being much time difference) but in boruto he atleast used it twice, and as he said, the more people the more chakra taxing it is for him, so we have to note that (despite it making not much sense) maybe anyone who enters the portal affects sasukes chakra, that's the only logical explaination, so I think he can use it the total number of times the kages, boruto and him (sasuke) passed