Your throat will absolutely not hurt if you’re a trained actor with a trained voice. You learn how to sing and speak with proper technique — years of classes — exactly so that doesn’t happen. Otherwise no one would survive on Broadway doing eight shows a week.
For an author who wants to narrate their own book though? Yes, if they don’t have vocal training. Which is why that might not always be the best idea, among other reasons.
One of the bigger reasons professionals are able to do broadway 8 shows a week is that they limit their voice to those 2-3 hours. Michael Crawford (who is the Phantom of the Opera to my ears) refused to sing at a tribute to him and the Phantom cast, because he had another play later that evening and didn’t want to damage his voice.
I firmly believe that even a trained actor would become strained after three consecutive ten hour days of constant speaking.
Well, as someone with friends on Broadway... I hate to tell you, but your belief is just wrong. Sorry :)
When you're rehearsing, it's all day long, for weeks and weeks. And once performances begin, Broadway actors are known to make further money during the day doing voiceover work since it fits their schedule, being one of the few acting gigs with a fixed, predictable daytime schedule.
Now certainly, you can't be belting high notes all day long. (Which may explain your story about Michael Crawford -- extreme singing is different, and that's a professional tenor range.) But a normal speaking voice? Absolutely.
That's also why, if you'll notice in the article, only one person is quoted as their throat hurting. Because for trained voiceover artists, it's simply a non-issue.
Fun fact: the vocal cords are one of the muscles in the body that don't ever get fatigued (similar to the diaphragm, heart). Which isn't to say you can't damage them (you can, with improper technique -- which is the case with most people without vocal training). But they don't "tire out" with use the way most muscles do.
For an author who wants to narrate their own book though? Yes, if they don’t have vocal training. Which is why that might not always be the best idea, among other reasons.