I farmed these for about 2 nights in a row, enough to get 2-3 stacks of them and maybe half a stack of high quality. Thank you for the notes on the leve rewards in Quarrymill. Thankfully, in my case, 2-3 stacks was just enough to get me through to linen. I used the leves in quarry mill to keep a decent stock of them.

To get through those levels, there is a leve you pick up in ul'dah for a velveteen cap of gathering or crafting and deliver in quarrymill. I found this very easy to HQ and the exp was more than your usual, probably because delivery was in Quarrymill (like enough exp to get almost half a level at 28 and 29). As more botanists are getting to levels 31+, the price of flax is going down.