that really depends
typically the dark the juice color and the sweeter the juice is the faster it's going to kill a coil
but it's cheaper to replace a coil then to replace a prefilled disposable pod

and a lot of times you can clean the coil and reuse it (as long as the wick didn't get burnt)
let the coil soak in water or alcohol over night then let it dry over night and it should be good to go again.
plus then you aren't limited to what flavors they have, you can pick up any juice you want to try (well depending on where you live and the laws there, like here in the us we won't be able to buy ejuice online anymore will have to go to an actual store and get it...but then again I do diy so not really an issue for me but it still sucks and is stupid for those trying to quit smoking)