Hour

Hours of operation and operating hours are the same.

Hours of operating is not idiomatic.

<....hours of verb+ing.....> <hours of possessive noun(ex)her)>
Do you see any expression as above? If any, can you teach me about it?

Thank you.

I'm sorry, I don't really know what you mean.

What sort of hours do you have in mind? "Her hours of studying had gone to waste, because she failed the exam anyway." Something like that?

the hours of her studying
her hours of study

Is OK,too?

eunjinnythe hours of her studying
her hours of study

Is OK,too?

No, those aren't natural at all.

The time she spends studying. The time she spent studying. The time she usually studies.

The hours she spent studying. The hours that she studied.

I think I saw a sentence beginning with 'their years of research~ ".
So i made 'her hours of work' from this example.
Could you tell me what 'her hours of work, and their years of research mean?

 If you look up at my post a couple up, I suggested something parallel to "Their years of research" and "Her hours of study."
You want to emphasize how long someone spent doing something, and that's the subject of the sentence.
The time they/he/she spent engaged in an activity: Her hours of studying went to waste because she overslept and missed her exam. Their years of research paid off w