Every day. Everyone should do that no matter how small you might think the achievements are, they are yours and yours alone and your struggles are you no more or less difficult than anyone else's.
Books in my case. Every year. I'm now at the stage where I can pick up any book in the series, turn to a page and know where I am and what happens next. Sad, I know.
Varies. Every 1 - 2 weeks. I'm the only one using. There are times I'm so busy, I'm using it only once or twice per day. There have been days when I haven't used it at all.