Hermione using the time turner in POA

[agreensaver]

No: HPFGUIDX 111443

Hi! newbie here...hopefully this hasn't been discussed to death already.

In the book Hermione is always dead tired because she can't finish all
her homework. What's keeping her from finding a secret room in
Hogwarts, locking the door, holing up for three hours, and then
repeating the hours with the time turner? Same goes for getting enough
sleep.

Also - although Hermione gave up on using the time turner after third
year, we would assume that she would continue using it had she decided
to keep the courses. So she would actually be repeating at least two
hours out of every day, from third to seventh year. Wouldn't someone
notice that she ages unnaturally quickly?
This might be a problem with people who use time turners routinely for
their jobs as well...