"You are right. But the day comes when you've had enough. Your mind can be spent, even if your body's not. We want to die. We need to."
Hamilton explains this to Will the night he gives all of his time credits to him. He is saying that death is natural for all human beings, and for people to live seemingly non-ending lives corrupts natural law and in so doing causes anyone to become corruptible with enough time.
"Is it stealing if it's already stolen?"
Sylvia says this to her father who cannot believe his own daughter is stealing time from him. She levels the conversation by revealing the truth that all of his time has blood on it, he's stolen it from the poor to satisfy his blood thirsty greed.
"A day. You can do a lot in a day."
Will gives this answer to Sylvia when she asks how much time they have remaining on their life clock. To her it must seem as the shortest time ever given to anyone, as her father has provided enough time for her to live forever, but Will makes it clear that to him 24 hours can be forever if they use it right.
