I have a Grace Original GMQ frame. I have it set at full size, 102" (8.5 Ft.) is the maximum size quilt that I can do on it. I believe the new Grace Pro is up to 120" (someone correct me if I am wrong, please). I leave it set up all the time. It requires about a half day of unscrewing and re-screwing a bazillion screws to take it down and set it back up..and then it has to be re-leveled. It is best to have enough room, IMHO, to have three sides accessible with at least as much room on each of the long sides to be able to bend forward and thread the needle or pull a tangle from the bobbin case, meaning you need some butt space behind you. A lot of people don't have enough space to access the back of their machine but even if you don't do pantos (which I think are a very important optional way to quilt) you can also use the bed on the back to tape down a stencil and use it to fill a block by using your laser or pointer. That saves having to mark the stencil on the quilt top. So two reasons to be able to access the back of the frame. On my setup I have a mid-arm Bailey (17" Pro) and there are times when I need or want to turn the hand wheel to get exact needle placement, so I need to be able to access the back for that too.
I have a very large alcove off my living room and it is my complete sewing area. I have one end of my frame up against the far wall in the center of the room as you look into the alcove and the end of the frame sticks out into the living room through the arched doorway by about 2 Ft. It's not in the way at all, my DD2 can easily walk past it to get to her bedroom which is off the alcove and we can easily access my bedroom door which is on the LR side of the alcove as well. I have an aisle on each long side of my frame. On one side of the aisle I have my sewing machine, cutting table and ironing board set up. On the opposite aisle I have my book cases and a file cabinet set up. It works for me for now. When my DD2 leaves for college this summer, I will move my frame to her room and that way I'll have two adjoining spaces in which to really spread out and get some work done. I'll miss her but I'm looking forward to more room ;)