Me too. 2 things though: a) I'm not sure what the difference is between extract level 4 and 5, and b) they both let you make permanent potions, but as far as I can tell in version 4.2 there's only one holy water so only one permanent potion can be made in the game... is that right?
That is correct, yes. The single Permanent Potion you can make will add ten points to a single stat.
AFAIK there is no point whatsoever to Extract lvl five, as the entire menu is available to you for Lvl 4.
As things currently stand, even Lvl 4 is a one-shot only skill.