Having worked in publishing I've been used to working in the evenings and at weekends doing submission reading. There was never really time to do this during office hours.  Because of this and the limited publication slots where we could place things I became a really tough audience to satisfy. You develop quite a focus when it's your time you're giving up - and the pressure of publishing means that even if you love something you may not get it through a business meeting. So if you're not fully engaged within the first three chapters then you're probably not going to be.