How he will go will depend on how the team is balanced.
If you have a 2nd row and LF who can do nearly a full 60 minutes. Then you only need one sub to rotate them on and off. Sia, Manu and Wilkin can do a full 60 if not 80 when needed. Laffranchi can fill all those back row roles. So that allows for them to have their rest periods.
So that's 3 interchanges
Then you can have 4 props or even 5 for some games, including the bench.
At 20 minutes each, thats a further 6 interchanges.
It's managable but obviously the more you can extend those periods then the more flexible your line up can be, to include a back on the bench or a 2nd hooker.