There certainly is some developmental progression from silent reading at oral reading speed to faster silent reading speeds, but it usually happens in late elementary school/middle school. For some perspective, the average adult reads at about 200-300 wpm silently (depending on which reference you cite), and about 150 wpm orally (out loud). So if one is able to read at above 150 wpm with decent comprehension, I would say that that is reasonably functional. I agree that it's more important simply to know one's own reading time requirements.
In addition to mckinley's time management suggestions, I would also recommend investing a little energy into finding an active reading strategy that suits the individual reader. E.g., SQ3R (
https://www.khanacademy.org/test-pr...at-active-reading-strategies-part-1-sq3r).
