I didn't do any more flying than was necessary to remain current with my clubs requirements, so in reality one hour per month. For me it was more important to focus on getting first time passes and my own timescale for reaching 150hrs wasn't restrictive in that I'm not planning starting ME/CPL/IR until August 08 (finished exams December 06). Your plan looks suitable if you feel that you can put in 3-4 hours per week night. I found that 1 hour study followed by a break of 15-20 minutes before starting again worked for me, I wouldn't have been able to do 3 hours straight through.