Before you face Duriel, go buy a bunch of stamina and thawing potions. 6 of each should be enough, you can do 10 of each for good measure. Drink them all right before you face Duriel.
Stamina potions give you 30 seconds of infinite stamina.
Thawing potions thaw you, and also give you a 30 second boost to your cold resistance.
The 30 second attributes stack. So if you drink 10 stamina potions, you have 5 minutes of infinistamina.