i keep my frame set up all the time - it would be a hassle to break it down and put it up as needed. i also think its good to practice a few days a week to keep your skills fresh.
i have the ability to do a king size quilt but i don't keep it set up for that size since i rarely make a quilt that large.
i keep my frame setup in the middle of the room so i can have access to the front and back.
i've seen some set back towards a wall because they never do pantos only free hand. if you only want to do free hand it takes up less space in a room.
my space is about 16x20 and i have a walk in closet. i have my room set up with all cabinets and counter tops/work surface along 3 walls and then the frame floats in that area.
i have plenty space to walk around everything.