The dose and time between IVIG may not be the same for everyone. 2gm per kg is a pretty standard dose for CIDP.
I started at 12 week intervals, then 6, then every 3 weeks (all 2gm per kg) I then did 1gm/kg every week for 12 weeks.
It depends on how long you stay stabile on your current plan, if not it may need to be altered.
I've also got other opinions, and found that each Dr, has their own ideas on how it works best as well.
As far as staying on it forever, that's not usually the plan , but it sometimes ends up that way for a lot of people. My doctor believed the only way to ever get off it , is to try to go without it for a while and see how you do.