Do you mean how long it will last until the juice is used up? The answer is: it depends! Everyone vapes differently and uses up juice at different rates. Its something you will have to get a feel for over time.
If you mean how long it will last before it dies (how many refills) again, it depends. Quality control for atties/cartos can be spotty. You may have one that lasts for weeks and another than dies in 3 days. It also depends on your
vaping habits as well. If the flavor starts to taste off stop and top up or change the carto out. Once the filler gets burned it can be impossible to get the burned taste out.