In our area, the schools go for 36 weeks. I plan 3 twelve week terms of work. While we don't have attendance requirements in FL, I'd be uncomfortable schooling less than the 180 days schools require. I do think the time is reasonable.
The first thing I do is sit down with a calendar and mark off any trips or big vacation day chunks and I plan around those. I start in September and finish in August with our year round schedule.
Typically, I plan 3 weeks of work followed by one week off. We take the off week to do whatever's needed - shoe shopping, dentist appointments, big projects around the house, fun things. However, if we didn't quite finish our 3 weeks worth of work, we do continue schooling albeit at a much lighter pace. I find it's a very good schedule for us. If I have closets that need organizing, but I know it will take a chunk of time, I know I have time for it within the month. That helps me not get so sidetracked.
We take ~ 3 weeks off at Christmas, 2-3 in the spring or fall and 2-3 before the new school year for me to plan. Later, I'll link our calendar for the 2013-2014 year. I find visual examples helpful.
Andream - start with the number of days/weeks you're required or need to school. Work backwards from there, penciling in weeks you wish to be off. You'll be able to see if your goals line up.