In terms of repotting to a different sized larger pot, African violets do best when they’re under-potted (the opposite of root-bound). Repotting to a larger planter should only be done when necessary. Repot your African violets to the next size up when the time comes. African violets that are root bound will show you symptoms including falling leaves and roots growing out of the soil. Monitor your plants for these signs and repot when you see fit. While you shouldn’t change your African violet’s pot size until absolutely necessary, you should switch out the soil about once a year. Replenishing the soil in your plant’s pot is beneficial in reviving the essential nutrients that are been lost over time.