It's stackable!
It lasts 1 round per 2 levels of the user. You can use it 3 times in a row, to gain 120% resistance to physical damage. At level 40, this will last for 17 rounds. A barbarian only needs to use it twice. 18 rounds is more than enough time to easily turn the tide of battle, when one of your characters is invulnerable.
Hardiness Bug?
hehe, to bad the magic resist one isn't like that, complete immunity to everything.....
If I asked, would you answer? Its your problem. Its a deep, deep problem. I have no way to ask about that... I have no elegant way of stepping into your heart without tracking in filth. So I will wait. Someday, when you want to tell me, tell me then. -Bleach
Just like Armor of Faith - but that's only level 1 
But seriously, do you heal if you're damaged while having over 100% resistance (like with elemental damage and resistance)?
But seriously, do you heal if you're damaged while having over 100% resistance (like with elemental damage and resistance)?
[url="http://www.sorcerers.net/Games/BG2/SpellsReference/Main.htm"]Baldur's Gate 2 Spells Reference[/url]: Strategy, tips, tricks, bugs, cheese and corrections to the manual.