We did this when I was pregnant and stopped about 1/2 way through. We knew we probably wouldn't keep up with it so we stopped. I semi regret it now but I also view it as another thing to keep up with and it would be even harder once we had #2
I love this! Was going to do something similar by writing yearly letters. My mom did this for me, talked about the year, what I liked, who my friends are etc etc. got all these letters at my graduation, it was pretty special.
Re: Cute idea