Should one read a fantasy series that has not yet been completed?

If you were reading The Wheel of Time fantasy series by Robert Jordan then you are unlucky as he has just died. Eleven of the twelve books of the series were completed. I read the first volume and judged it not interesting enough to continue but this is a best selling series. In the thrift store on Friday they had many copies of his books, maybe someone had a premonition?

I have read two books of the Song of Ice and Fire series by George R. R. Martin. I like these books, they are complex without being overwhelming. If you think about the plot too much you can guess what will happen, but they are great books for the plane. But the series is not complete. The author is 58 years old (the same age as Jordan). I wish he would just finish those books so I can feel safe reading some more. I get annoyed when I read on his blog about the time he spends not writing and making deals, but then I feel mean when I hear about him missing worldcon so that has can do more writing. Basically I should never have started an unfinished series. Another reason not to do this is that you end up buying hardback copies of the books as they come out.

Obviously Harry Potter was an exception to this rule, but it's finished anyway.