Not seeing friends or being able to spend much time with them makes the time spent together more valued and treasured. Long visits from friends can cause problems, disdain, impatience, or criticisms unwanted or unneeded and can cause friendships to end.
Kind of the same thing as the old adage attributed to Benjamin Franklin — “guests, like fish, begin to smell after three days”.
Maybe with friends, you can go one more day. Maybe not.
The real question might be, “How many short visits does it take to make a long friend?” Or, “How many long visits does it take to unmake an old friend?”.