With vampires, I always imagine they would be able to sustain a large amount of damage, as long as they have blood to heal with. What a person could do to an old vampire is breathtaking.
From Protector of the Grey House:
“He healed himself and they pulled his skin off again. Halfway through, he broke. Told them I was sleeping with Vincent but that his own boss didn’t trust me. He had been sent to spy on me to reveal my betrayal so that I could be exposed. His words helped my story, but then he told them what I had done in order to try and convince Vincent of my loyalty. The Slayers weren’t pleased to learn that I killed their kind. They had stopped interrogating him at that point. There was no reason for Wayne to keep talking. So why did he? Did you tell him to sell me out? Do you want to get rid of me that badly? Or is it just that your man was poorly trained?”