I knew Lucien would get back to the shelf life issue and want to turn Eli. But it would be foolish at this point. He still has to fool the Vespers so he can free Lucien.
Just being able to get him outside after so long has been an incredible gift.
Vane's cruelty has been supplanted by Cameron's calculated kindness and reward system. Conditions are better, but the cost of being there hasn't changed much.
I think you are taking the term break too literally and placing too much importance on it. Think of it like a deadbolt. They all leave and it's unlocked. They come back and it's locked again. It's only a redundancy. One thing won't release Lucien, and all of the wards have to be down at the same time to free him .
Lucien has no need to completely drain anyone for blood.
If you've read any of the Gone From Daylight series, those vampires prey on criminals. And there are some who freely give blood just as Eli did here.
It was a problem in all major cities back in the day. In NYC, it was put on Barren Island to be turned to fertilizer. You didn't want to be on the wrong side of the wind of that place.
The cost of Lucien's freedom is unveiled, and it's high. The four family bloodlines are non-negotiable deaths and likely Kylie.
Lucien's love for Eli is both deep and true. He is willing to endure rather than hurt Eli.
There are so many things which can go wrong.