Heroes Star: "Claire Is Indestructible, but...."

Addressing some confusion and much speculation in the wake of this week's Heroes episode - in which Future Sylar appears to gain the upper hand on "Cheerverine" Claire - Hayden Panettiere on Wednesday afternoon offered TVGuide.com her own, well informed take on her alter ego's mortality.
Acknowledging that whether Claire can actually suffer a life-ending injury "is a question that was never really answered for me" by the show's powers-that-be, she says, "I think that she is indestructible - she can jump off the highest buildings, and she can go through a wood chipper and be fine - but I do think that there is a reason why she was so scared when Sylar came along, there's a reason why Peter has to save her.... 'Save the Cheerleader' obviously means the opposite of having her die."
What exactly, then, might be any hero's Achilles heel? What might offer the final nail in the coffin for Claire or any regenerator? Offers Panettiere, "There is one spot on the back of your head, near your brain, where if we do get stabbed" - as has happened to both Claire and, very recently, Peter - "we have the ability to die. The question is, how long could we [be stabbed] there before we were no longer able to regenerate? That's a question I still have." And one we hope present-day Claire doesn't have to answer soon! - Reporting by Matt Webb Mitovich