I've done a medium stipple on a twin size quilt in a day that was also filled with doing laundry and other chores.
I've also worked for 15+ hours on super tight, micro stitching for a 12" square. So there isn't really a time it takes to quilt, it totally depends on what I am doing.
Charity lap quilts usually take me 3 hours to quilt. I just do an all over pattern, not usually stippling.
The key is to have a plan- how are you going to move in and out of blocks? And to have a really good support for the quilt. I put an out-feed table behind my machine, and set an ironing board to the left of my machine table. No part of the quilt is unsupported.
I also don't roll, I bunch.
Leah day does have some videos on how to quilt giant quilts.
http://www.youtube.com/watch?v=7-eOp...source=message is a good one to see. If she sped it up 8x and it is a 15 minute video, this quilt took her 2 hours.
Even though all of her designs CAN scale up- I think many of them don't work nearly as nicely on large scale, because they are filler designs. Most bed quilts don't need filling designs.