Currently, shipping for subscription orders are on a fixed interval and cannot be changed.
Here are the fixed intervals:
72g Toothpaste = every 10 weeks
188g Toothpaste = every 6 months
10g Toothpowder (6-week travel size) = every 6 weeks
25g Toothpowder (3-month tub) = every 3 months
51g Toothpowder (6-month jar) = every 6 months