I'm not so sure there is such a thing as "normal" :-) I have frags that have grown into colonies pretty "quick" (1-4 months), and I have frags that have done nothing in 4 months!
Here's a tri-colour I ordered online back in June of this year. It was a 1 branch 1" frag.
Today it is a nice little mini colony.
Here's a 1.5" christmas millepora frag I got back in August 2009. This picture was taken August 29th.
Today (just 8 weeks (ish) ), it is a nice colony.
All of my bird's nest frags tend to be quick growers like this too but I also have a few frags I got back in late spring (june ish) that haven't grown a millimeter :-)