You've disproved a point no one made. No one here said the first feeding isn't usually lethal. You said feeding is usually lethal. It's not. Thomas explains why at the end of Turn Coat. Also, Thomas was wrong. Bigfoot on Campus proves that.
In my opinion, you totally misread Thomas, he has been fighting what he is for years.. That is what Margaret meant in the soul gaze between Harry and Thomas, that he is tired. It is the point that Lara was making to him for years, humans are prey, kine, food.. The Skinwalker awakened that in Thomas. Thomas up until then had been different, not wanting to feed until death...
But here is what he says at the end of Turn Coat. Page 413
"Then talk to me," I said, urgently. "Thomas, Jesus Christ. This is notyou." "Yes, it is, he spat, the words a bladed hiss. "That'swhat it taught me, Harry. At the end of the day, I'm just an empty place that needs to be filled." "I didn't want to kill those girls. But I did it. I killed them over and over, and I loved how it felt. When I think back on the memory of it, it doesn't make me horrified." He sneered. "It just makes me hard."
He points to a woman and a child and says that all he sees is food, then he references tigers and how he feels.. page 414
"I'm. . . not wandering around blind anymore. Not trying desperately to be something that I am not." He looked back down at the tigers. "Something I can never be."
He goes on to say that killing the kine every time would be stupid, but it goes against their nature.
So yeah, they will feed until death when they can... No problem.. When the Skinwalker mangled her guards, did Lara call an ambulance? No, she ate well that night..