Where is all the liquid luck in the Battle For Hogwarts?

Here's a question that has been bothering me for quite some time now: why did no one involved in the Battle of Hotwarts at the end of The Deathly Hallows take a nice dose of Felix Felicis before the fight started? Seriously.

Professor Slughorn introduces us to this wacky substance in the Half-Blood Prince. As you will recall, Harry gave his stash of Felix Felicis to Ron, Hermione and Ginny just before heading off with Dumbledore to Voldermort's cave to attempt to retrieve the locket Horcrux. They later credit the potion for saving their lives throughout the fight with the Death Eaters who invade Hogwarts that night.

Sure, it takes six months to brew. And sure, it is devilishly tricky to make and a disaster if it goes wrong. But Slughorn has proven himself capable and surely Snape himself should be able to brew the potion so why aren't at least some people on either side of the final battle flying on liquid luck when the fighting starts?

It's possible some are, in fact, under the influence of Felix Felicis at that time and J.K. simply decides not to tell us readers. Or, perhaps, she conveniently forgot about the potion when she wrote the seventh book because, let's face it, liquid luck would kind of undermine the drama of the final book, wouldn't it?

And that is, of course, the problem with narrative short cuts like this. Rowling needed a convincing, magical way for Harry to weedle the Horcrux memory out of Slughorn in Book Six and decided to create Felix Feilcis to accomplish that task. It sounded good at the time and even produced some fun moments. But, once she'd created the a potion that brings luck to those who drink it, she kind of found herself in a bit of a pickle in the seventh book.

Now that they know about Felix Felicis, why would Harry, Hermione and Ron not brew a batch while they're holed up at Grimmauld Place, then take a little dose of it each time they go into a particularly dangerous situation: like the Ministry, Gringott's or Hogwarts? Or, for that matter, why wouldn't one of the adults in their lives have brweed some Felix Felicis and delivered it to Harry? After all, he is their best hope for defeating Voldemort.

Yes, overuse of the potion can lead to ill effects but we have it on good authority (from J.K. herself) that Slughorn had used it twice in his lifetime with no problems and, further, that Dumbledore had used it too in his youth, though only for recreational purposes of course. So what's the issue?

This question bothers me a lot. It undermines the tension of the final book and makes me wonder why Felix Felicis isn't used more often by more witches and wizards. My personal opinion is that Rowling would have been better off finding some other way to get Harry together with Slughorn in Book Six and to let Harry's natural charms and kindness work on him rather than creating a potion that would prove so inconvenient, so counter-productive to the creation of tension in the seventh book.

I find I have to forget about the existence of Felix Felicis in order to enjoy to its fulleset the seventh book. And that's not a good sign.