Clark clearly needs someone who needs the whole story. His parents know he and Lois aren't in love, so they're able to talk with him about taking time to build a relationship and make things work. And he does know they're right, and he does want to make things work. But they don't know that he's thinking that "making things work" means "making things go smoothly for the next five years."
He needs someone to disabuse him of this notion that he can walk away in five years, hunky-dory. Even if he and Lois don't fall in love by then, and get divorced (can't believe I just wrote that!), their lives will still be intertwined with the child. So he should suck it up and take one day at a time, and stop staring at a hypothetical cutoff date.
