Your pup will let you know when to cut back. When Tucker was a puppy, he had no problem eating 3 times a day until he was about 6-7 months old, which is when he started losing interest in his second meal of the day and would barely even touch it. That was when we cut him down to 2 feedings a day and switched him to adult food. He started getting 1 cup in the morning when we got up and 1 cup in the evening.
We feed 3 meals/day until about 6 months. Unlike Jo's Tucker, Brady still ate all of his second meal, so I gradually decreased the lunch and increased the breakfast and supper over a few days to wean him from it, so he was still eating the same amount just in 2 meals instead of 3.