I fall in the “not” category (the average-sized book is a 3-4 hour length for me), but I will occasionally intentionally subvocalize, just to slow myself down a bit.
I've wondered if this is one of those thing that if you have not learned how to do it before a certain age, your brain can no longer learn it, like seeing in stereo etc...
Once I found books and authors I liked I became a voracious reader, from eight to adulthood it wasn't unusual for me to have 3-4 books on the go at once and to read 3-4 books in a week all the classic works of sci-fi, books on science, computers, geography, history, politics, biology I was a sponge, I'd read almost anything - I used to read while walking to and from school, I walked into surprisingly few lamp posts.
The more I read the less I vocalised the words in my head, I started with pointing at each word (as most kids do) and then I stopped doing that, then I started looking at the word shape rather than the word and not vocalising it at all, it wasn't anything conscious just a natural progression.
In a very profound sense that teacher and my mum altered the scope of my life for the next 30 years, the teacher by realising I just needed the time and the right material and my mum for scouring charity shops/2nd hand book shops to keep me fed with books as money was tight (bless her, she used to keep a list in her purse of all the authors I liked, what books they had written and which I'd read).
This is what I do, though sometimes it's a second pass over a passage that I want to savor or really focus deeply on.
I've read all of the Discworld novels at least 3 times and a few like Hogfather more than a dozen (I re-read it ever Christmas).
Reading is one of lives truly great pleasures and it's one of lifes most democratic.
Can on learn not to subvocalize?