Forged Documents

It will always reset at midnight without regard to the time of day. Don't have to worry about using it in 24hours intervals =D

Edit - (Fixed some grammar)x2

Here is the math to see where this recipe would "cap" herb prices:

40s = rep-discounted resilient parchment price
10g = conservative forged document average (sounds like it goes up to 30g, so it may be more like 20g average)
3 blackfallow ink = 1 stack of 20 high-end herbs, since they net 6 pigment

You should only buy+mill herbs to forge documents if:
(Cost of forging documents) < (Profit from forging documents)
40s + 20*(1 high-end herb price) < 10g + (1 inferno ink)
20*(1 high-end herb price) < 9g60s + (1 inferno ink)
high-end herb price < 48s + (1 inferno ink price) / 20

Low-end herbs get 5 pigment per stack instead of 6, and generate half an inferno ink per stack:
low-end herb price < 48s * 5/6 + (1 inferno ink price) / 40
low-end herb price < 40s + (1 inferno ink price) / 40

You can use blackfallow ink for other things, so you also want to make sure it's cheaper to craft than your profit from the forged documents:
3 blackfallow < 1 forged documents = 10g - 40s (parchment)
3 blackfallow < 9g60s
1 blackfallow < 3.2g
AND Backfallow Ink is worth < 3.2g

10 Blackfallow can be traded for 1 Inferno ink, so you also want to make sure:
Inferno Ink < 10 * blackfallow ink value
AND Inferno Ink is worth < 32g

Considering the glyph and Darkmoon card markets, it won't be worth spending inks on forging documents any time soon. Even late in Cata with a huge herb supply, lower glyph prices, and lower demand for these mats, I don't think forging documents will cap herb prices. Each scribe can only forge 1 set of documents a day (1 stack of herb) -- there aren't enough scribes to forge a significant percentage of the herb gathered daily.

That said, this recipe is one of those knobs the designers could turn to increase herb prices later on -- either by increasing the sell value of the forged documents or by lowering the cooldown.

Because Blizzard made glyphs permanent, they added a couple of ink dumps to the game to create a flooring price on ink
One quest has a guaranteed return, the other is a random gamble.

The forged documents starts a Quest that provides reward that can act as a ink dump for inscription:
The quest rewards generate roughly 10 gold, for 3 inks and a parchment.

The other ink dump is the Random Fortune Card with the ability to be redeemable for anywhere between 10s and 5000g.