It would be really nice would be if you could dictate your delivery date.
This could not only help people with different schedules, but also allow a lot more nuance to the subscriptions. You could for instance, get 24 bottles every 5 weeks delivered on Thursday.
Or 28 bags delivered every 3.14 weeks.
Or pausing a subscription if you go on vacation, and resuming it the day you come home.
Scheduling a delivery for an exact time (8:30AM on Tuesday) might need to wait till drones, and fedex might not have consistent delivery times, but adding a calendar to the subscription screen to choose the ship date should be doable.