I can only tell you our experiences.  My dd could not read, could not remember a simple 3 letter word from one sentence to the next at 7.5 or 8 years of age.  We home school so at her end of year evaluations she always showed very minimal improvement.  BUT it was improvement.  She would get so frustrated, say it was too hard, hold her head, tell me reading hurt her head, she’d put her hand over one eye and give up after 1 or 2 sentences saying she couldn’t do it.  And with her control issues – there was no way I was going to get her to try again any time soon.  Her eyes jumped and she had issues with convergence.  
We did NR with Bette for 2.5 years and no other therapies (couldn’t afford any).  Her math improved faster than her reading  she was only behind 1.5 grade levels in Math.  We would read Bob books and she still struggled.  At the end of 3rd grade which was last year she was still reading at at primary level.  She continued  to switch letters in words, switched b and d longer than I thought a 9 year old should. Her comprehension when I read to her was better, but we could only read for 15 min at a time or she couldn’t focus.  Slowly, ever so slowly, she improved.  One day about 6 months ago, she said, “MOM, the letters aren’t jumping around anymore.”  Well, she never knew they weren’t supposed to until they didn’t.   She graduated from her NR program in Jan and she has made gains by leaps and bounds in reading.  Math too, but her retention, comprehension, her ability to process and really READ is infinitely better.  One of her eyes still jumps a bit so she does keep a ruler under the line she is reading sometimes.  Her end of year home school evaluation is in June but I know she will be pretty close to grade level (4th).  She has made such strides in reading in such a short period of time that I am having to backpeddle to catch her up in spelling (spelling and phonics rules)  – we never had to worry about that before because she couldn’t read let alone pronounce words.    
She will be 10 in May and I was beginning to think she would never even get to “average.”  Now she just needs to become more confident in her new abilities”.