That depends on how often you hit it, how long of a puff you take, and which coil you are using. Nobody can really tell you how long it will last for you, that is just something you will have to test for yourself. Though with it being a 900mah battery, i doubt you will be measuring it in days. But if I had to give it a guess, I would say it could possibly last a full day on a single charge if you are a moderate vaper.
The coils could be cleaned, but as mentioned above, it would likely cause a noticeable reduction in flavor.