Seven days is the magic retention threshold

Once you get to seven days, loss aversion kicks in, and you retain. Going from a one to a two-day streak, huge jump in retention, two to three day streak, slightly less but still huge and it's up until day seven.

Give more flexibility when a user is starting their streak. Eventually, once people get on long streaks, you don't want to give them as much flexibility.

We're giving people kind of some other reasons to do a thing that they may want to do, but they don't necessarily have the motivation to do it right away.