Depends on the liquid you use. I have several evods, the ones with menthol or extreme ice would normally go through 20-30 tanks before i felt the need to change/clean the coil. My evods with sweet liquids or with coffee liquids needed to be cleaned or changed every 10 tanks or so. I don't dry burn my coils when i clean them. I remove the center post and extra wicks, then run warm water across the coil. After that it goes into a vodka soak for an hour, them to dry out for a few days until i need the coil again. I normally get 5 - 10 cycles from each coil before toss it into the pile for later consideration or rebuilding.