Like a regular brush head, you should replace your mouthpiece every 3 months. With the Willo subscription, you don't have to remember to replace your mouthpiece - we will automatically send you a new mouthpiece every 3 months with 2 rinse pods (aka toothpaste) directly at your door.
So, concerning the beta test program, you don't need to worry. You should have everything you need in order to brush with Willo for 3 weeks :)