I learned to speed read, last years I'm using it less and less
Learning something and don't using it regularly, that can be worst thing for your productivity. If you learn something new, you should never stop doing excercise with it. That's the best way not forgeting that something you learn.
In my opinion, you don't need read very fast. I think nobody does. If you not satisfied your reading speed, so let it slower. There is no reason to read faster if you don't get better comprehension or another something. It only gets more time but why should I need more time If I don't understand what I'm reading.
200 - 250 words per minute is normal, relaxed reading speed. So make this speeding test.
Also read How can I improve reading speed and comprehension?