Getting Ready for School

I occasionally buy workbooks for Jerilyn to practise writing. However, her interest lasts as long as the smell of a new book. After writing and scribbling few pages, her interest fades and the book has to be shelved for at least a week before one day, she happens to spot it from the shelf and starts scribbling again. This is so except for the 2 books which I bought about 2 weeks ago.
The moment I bought the books, she has been doing the exercises non-stop. She is so engrossed with the exercises that she spends 2-3 hours each night on the exercises. On the first night, she didnt even have breaks in between. I was the one who had to stop her as my eyes were already drooping. When it is time for bed, she insists on taking the books with her into the bedroom and won't stop writing 'til we turn off the lights. She is so into it that right after waking up from her afternoon naps, she says "I go down to do my work, ok?" There was once she immediately sat and started doing the exercises the moment we came home from shopping.
The 2 books are published in Singapore. I have a few books of my own which were bought in Singarpore many years back and indeed, there are still one of my favourites. These 2 books are as appealing to my daughter as those books to me. In short, Singapore published books have better quality thus more appealing to readers?
It seems like she is preparing for school. She always says that she is attending school (soon) and calls me 'Teacher' while she is my student. After each exercise, she wants a star to be given. She thanks me very loudly with full sincerity. When she makes mistakes and doesnt get a star from me, she sulks.
Wondering if most children go through this stage where they show extreme enthusiasm in studying and schooling.