<question 1> i bought some prefilled cartos, but i can't tell when to change them? i've tossed a couple thinking they were out of juice but wasn't really sure.
i am also about to order some empty carts and juices. <question 2>when will i know to refill and when to replace the carts?


how do i know when i have topped off the cart when i am refilling?
i am also about to order some empty carts and juices. <question 2>when will i know to refill and when to replace the carts?
how do i know when i have topped off the cart when i am refilling?
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