My wife and I are playing through a second time and we are sneaking into areas that we are not required to go yet as much as we can! I even got really gutsy and (SPOILER)ran through the Necrohol of Nabudis at level twenty-seven to get the Zodiac Spear.

She took care of the getting through the Wyrm's Nest so I do not know exactly when we got through it, but it was after (SPOILER)Raithwall's Tomb.