Slim’s advice can be distilled down into a couple simple ideas: that it’s important to strive to be a good person, and that it’s also important to slow down and try to enjoy happy things. Doing these two things, Slim implies, is what kept him from wanting to die. Telling the boys to “do their time before it does them” is another way of saying that people have a choice in how they experience their lives. They can choose to focus on the good parts, and if they don’t, it’s all too easy to feel powerless and pessimistic about life. At this point, it’s hard to tell whether Eli is internalizing these ideas, or whether he’s too busy idolizing Slim to grasp his meaning.