My study in Switzerland was pretty intense. Class began at about 8:30 every morning and went until 1. There was une brève pause from 10 to 10:30. I was still working on east coast time, so my studies began at about 3 in the morning and finished around 7. Much to my tutor's amusement, I spent the first half of class just trying to get my head in the game. I would have an exercise, know the answer, and take two minutes to actually bring it out. In the afternoons there was often some sort extracurricular activity. I went out to a vineyard on Wednesday in the small town of Aigle. Best wine in the world.
What I picked up from my study is what I already knew--acquiring a new language is hard, and people who claim that you can do so inside of a year without changing anything else about your life probably have their hand in your pocket. It isn't to say that no one can do it. But if you're going to learn a new language you should expect a fight and gird yourself accordingly. You should even expect it to be hard if it's your child.
My tutor here in the States learned French when she was six at an immersion school. Her recollections of picking up French are bracing: long periods of not knowing and knowing you don't know; French teachers yelling at you for doing something wrong, and you not being sure what it was. My son has just started his French studies (his request, not mine) and they're going to intensify over the summer, so I expect him to get a little bit of the same. It's obviously true that it's easier to acquire language when you're younger. But this has no meaning to the individual experiencing it--your only frame of reference is your own skin.