The Ramchal explains that the answer lies in the Egyptian's intent, which became clear when it was time to let the Jews go. Had the Egyptians done it with the intentions of merely doing G-d's will, they would have immediately let them go when the situation warranted it. The same is true of our lives: We can sometimes justify not giving as much, not volunteering enough, or not learning enough Torah by claiming not to have time. The truth comes out, though, when we DO have time, on weekends, vacations, or between jobs/school. If we do what we can WHEN we can, we will prove our appreciation for the Torah, and grow our appreciation OF the Torah in the process.