There seems to be a mixture of responses here, I started ground school DL in Jan this year and have my first couple of exams coming up in around a months time, I am taking my time and stretching out the full 18 months. I have been doing about 2/3 hours per month, as said previously, I think anymore for me would infringe on getting the balance between work/flying and family, but it all seems to be working well at the moment.....and I actually enjoy the studying (at the risk of sounding like a sick pervert!)