Avoiding an unfinished series makes you miss what is there. I'm specifically thinking of Rothfuss. I really wish the third book would come out but I'm glad I didn't wait for that. I would have missed the enjoyment of sharing insights with fellow readers and crowing when I guessed right (and remaining perfectly silent when I guessed wrongly - "nothing to see here...move along").

I can't imagine you are 'religious' about this. If so, you could never read any book that identifies itself as the first of a series.

You'd have to have not seen anything Harry Potter related for 10 years (until 2007) while everyone else was talking about them.

You'll lose years of enjoyment waiting for the Stormlight Archive to complete.

You could die first.

You're permitted to enjoy the moment! :)