GC for parents based on I130 + I485 + AP

[gcfool]

I am USC and I am planning to file GC for my parents. After reading many threads in this forum, i see that senior member "Peace" has been recommending CP over AOS. My parents are already here with me in CA and I would like them to stay with me untill November, 2007. Their B2 is valid until August, 2007. I haven't had any luck applying for extension in the past and one thread in this forum suggests that applying for B2 extension after I130 won't be approved. It looks like i can't apply GC based on CP because this doesn't allow my parents to extend their stay. On the other hand I485 processing times are unpredictable. I trust that some one in this forum will throw some light on the following questions.

Is the family based I485 given higher priority over employement based I485?
What is typical time taken for family based GC based AOS at CSC?
Is it a big risk that this family based I485 could take forever to approve?

Thanks
gcfool