Sounds like the client has you trained. Everything the client asks for, you give in. What do you think the client is going to keep doing?
Its like giving a dog a biscuit every time it pisses on the rug.
Still, I feel that the fair solution to both parties is to explain to the client why the important and urgent items are going to take much longer than he thinks.
OP could look on this gig as an opportunity to train himself in managing clients, and therefore walk away with some benefit.