instead of 52 cards, let's try 10.
for 10 cards, if you break them in half and then perform the ripple shuffle,
the top card could be anywhere from the top of the deck to the half way point (the 5th card.)
however, ending at the half way point would be the worst case senario, as when you cut to shuffle again, the middle card is on top again.
my guess then would be 3. once to get the top card close to the mid point, another to get it a good distance toward the bottom, and then a third to finish the possible transition.