This article has been recently updated!
Great question! We get it a lot. And now, we're happy to say - yes, yes they are. We've just released the KININ Eco which is a pod-system that you can use refillable cartridges in.
The original diffusers we sell last about 30 days, but are not refillable. They are still available for sale, but ultimately we'll be discontinuing them and moving to the Eco. If you'd like to be notified about this, please leave your email address here, and we'll notify you once we launch the refillable product.