This seems like a very simple question. At the very least, it should give you an idea. How long does it take? There are many reasons to change your coil.
Let's take a closer look at each.
After you have smoked a few e-liquids, your ability for the coil to deliver its flavour will decrease. This can be subtle, almost invisible, or dramatic. The best refills are usually the third or fourth. The flavor will begin to diminish. Variables can impact the amount of time that the flavor will remain acceptable. The quality of the flavor depends on many factors including the type and structure of the coil, the wicking material, the temperature of your coil, and the flavourings. Some people may get bored quickly while others will enjoy it as long as it delivers the nicotine they desire and produces vapour. The flavour will become less enjoyable over time. This is the moment they must replace their coil.
Simpler flavours, like mint or lighter fruits, can extend their flavour life. Contrary to heavy tobacco flavours desserts and bakery flavor (which unfortunately are my favorite) tend to lose more flavor.
It is possible for the vapour production to experience a similar drop of flavour. It could occur alongside the loss, or it may happen independently. It can be frustrating to notice your e cigs UK producing less satisfying vapor than you used.
Variable wattage can be used to boost the power. This will sometimes produce more smoke and last longer. But, this will decrease the coil's lifespan. Your coil should be replaced if you experience a substantial decrease in vapour.
It's important that you remember that if your coil smells burning, it is most likely because it has been burnt. Once the wicking materials have been scorched or singed it is difficult to restore the flavor.
It is possible to cause damage to the wick by improperly priming the coil and using less than the recommended power. It's time to replace it once it has melted.
This is an issue that is somewhat like a burnt flavour, but the coil will produce e-liquid "caramelisation" as it is used. It is not caramelization but it will still work as a description. It is normal for white cotton yarns over time to turn brown. If your coil starts to taste sour, it's time to replace it. If you smoke dark or very sweet tobaccos, it may be necessary to replace your coil quicker.
There is no clear answer as to when it is best to replace your coil. There are two options. Either you'll know when or "when you feel it necessary". None of these options will satisfy a brand-new user of an ecigarette.
Some people might be content to change the coil only once or twice per week and still enjoy the fresh, clean flavor. Some may be able maintain a coil for several weeks, or even months, depending on how clean they use liquids. If this is the case, it's a wonderful thing. It might be worth looking into a new device which has different coils or uses a different liquid flavor.