I don't believe anyone has covered this and I'm seeking clarification on The Sensai.
1) Do The Sensai cards replenish during play? If player A obtains a sensai card, does a new card take its place?
At the end of each round, any that are not taken are cleared off and a new set laid out.
2) Do the discarded Sensai cards eventually get reshuffled to be a new "large pile"?
Never. There are enough to get you through the whole game. They have a different setup than the other cards.
I ask this because in the side bar of the manual, it mentions Dojo cards and Guard cards depleting and to reshuffle them for a new pile, but nothing really states it for the sensai cards.
It is under the 3rd "point" (resetting the sensei) under Ending a Round on Page 9. Pretty clear here.