Jack (age 5) is up to lesson 17 in Teach Your Child to Read in 100 Easy Lessons. Last time we did it I think he was getting a little overloaded. He keeps forgetting that the "i" makes a short vowel sound like in "igloo." I asked him if he wanted to do it tonight before bed, and he said yes. But he wasn't concentrating, he kept talking about other things and looking away.
Which is why I'm not going to ask him if he wants to do it anymore. When he wants to, he'll ask.
When he asks, he is motivated, he concentrates better, and he goes more quickly. Instead of trying to coax him every day, I'll wait for him to come to me.