Tyson - I use IVIG as a treatment to keep me going. I don't wait until I feel like I'm about to fall out to get a treatment. I do stretch the treatments out more if I am feeling great, but have no problem backing them up if I start to feel worse. I did 1 day/week for several months and about 2 months ago, stretched it to every other week. I tried going to 3 weeks, but started feeling weaker, so I went back to every other week.

If at all possible and if IVIG helps you, you need to talk to your doc about setting up a routine of IVIG - when you do it routinely, you usually don't have to do 5 days at a time to get the benefit. As I said, I do 1 day every other week right now.
For others, it might be 2,3,4 or 5 days to get the best benefit for them. It will probably take some experimenting.

Good luck!