Thanks! Good questions.
The original version was 21 days in an attempt to help players form more long-term habits, but in playtesting, I got feedback that it was discouraging for a significant number of them. One week seemed to be the sweet spot, and that way, players who really need help can start small. From my perspective, even a single intentional decision on the log is progress. I say, finish a week, check in with yourself, and start a new week if it feels motivating and beneficial.
Sure, I think more self-reflection is always better, and some might like having it encouraged throughout the week. In a future version I'll add some language to support the option for adapting the game according to player preference. Thank you so much for your feedback!