You know you don't have to start 5 topics right? It's just 5 posts total...
Anyway, again the answer is it depends. Mainly it's going to depend on the
juice you are using. A thicker darker sweeter
juice will gunk up your coil heads faster than a thinner clearer less-sweet
juice.
If you clean them regularly, say about every 2-4 refills, you should be able to get a couple of weeks to a month out of them. You'll know when it's time to change them as the flavor will be muted and the vapor will become light. You might also notice a slightly burnt taste.
Youtube has a lot of good videos on how to clean and dry burn a CEx clearomizer.