I use Aspire CE5s along with several other types. I vape licorice, butterscotch and cinnamon roll in rotation along with a few other flavors. The first symptom that the coil needs to be changed is a loss of flavor. The second is the coil seems to be clogged causing you to suck harder to get the same amount of flavor and vapor. A light dry hit may make little difference. It it is a heavy dry hit nothing will get rid of the burning taste from the wicking material and coil. Time to toss it. Sometimes, not often, the taste of the dry hit gets into the eliquid. If that happens pouring it out and cleaning the tank is the only solution.
Some unsolicited advice. When you buy new coils be certain they are authentic. Just because there is a scratch code on the box does not mean the coils are authentic. I know better and it happened to me. Checked the code on the Aspire site. The number had been checked 841 times. The first coil in the pack was put in the CE5 day before yesterday. It is so clogged I need to change it now. I can normally use the coils several weeks. I imagine the remainder of those coils are the same, essentially useless. Kiss that $10.xx goodbye. No one to blame but myself.
You can check for good vendors by going to the Forum Suppliers forum from the link near the top of the page. You can also use the Search box that is toward the top of the page. If I see 5 negative comments out of 100 I put that in the stuff happens category. Excessive negative experiences will get the supplier removed from the forum suppliers forum.
Happy vaping!