It wasn't time-travel (which through Time-Turner can only go back an hour per turn, 6 times used in total), it was repeated Obliviations of Hermione.
It was Obvliations in this case but don't be confused by the limitations in time travel. When it comes to this kind of task, one days worth of turner use done smart and with preparation would give more information than a month of constant obliviation use, without the pesky side effects of death by starvation, dehydration or sleep deprivation.
Similar strategies would give Harry a full index of the entire Hogwarts library ranked according to a reliable indication of potential usefulness, difficulty level, and possible risk. Even with the crippled turner as he currently has it, if Harry was out to win and not tell interesting stories, he probably would have won already.
He tried that, a while back. Ontological loops just give him "DO NOT MESS WITH TIME."
(The HPMOR discussion thread after this one is here.)
This is a new thread to discuss Eliezer Yudkowsky's Harry Potter and the Methods of Rationality and anything related to it. There haven't been any chapters recently, but it looks like there are a bunch in the pipeline and the old thread is nearing 700 comments. The latest chapter as of 7th March 2012 is Ch. 77.
There is now a site dedicated to the story at hpmor.com, which is now the place to go to find the authors notes and all sorts of other goodies. AdeleneDawner has kept an archive of Author's Notes.
The first 5 discussion threads are on the main page under the harry_potter tag. Threads 6 and on (including this one) are in the discussion section using its separate tag system. Also: one, two, three, four, five, six, seven, eight, nine.
As a reminder, it's often useful to start your comment by indicating which chapter you are commenting on.
Spoiler Warning: this thread is full of spoilers. With few exceptions, spoilers for MOR and canon are fair game to post, without warning or rot13. More specifically: